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<!--Modified on: 11/8/2011 8:39:49 AM-->
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        <link:definition>06042 - Disclosure - Acquisitions (Details Textual)</link:definition>
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        <link:definition>06041 - Disclosure - Acquisitions (Details 1)</link:definition>
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        <link:definition>0604 - Disclosure - Acquisitions (Details)</link:definition>
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        <link:definition>0504 - Disclosure - Acquisitions (Tables)</link:definition>
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        <link:definition>0204 - Disclosure - Acquisitions</link:definition>
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        <link:definition>0612 - Disclosure - Subsequent Event (Details)</link:definition>
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        <link:definition>0212 - Disclosure - Subsequent Event</link:definition>
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        <link:definition>0607 - Disclosure - Debt Obligations (Details Textual)</link:definition>
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        <link:definition>06091 - Disclosure - Long-term Incentive Plans (Details Textual)</link:definition>
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        <link:definition>0509 - Disclosure - Long-term Incentive Plans (Tables)</link:definition>
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        <link:definition>0609 - Disclosure - Long-term Incentive Plans (Details)</link:definition>
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      <link:roleType roleURI="http://quantaservices.com/role/PerShareInformationDetailsTextual" id="PerShareInformationDetailsTextual">
        <link:definition>06061 - Disclosure - Per Share Information (Details Textual)</link:definition>
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        <link:definition>0209 - Disclosure - Long-term Incentive Plans</link:definition>
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        <link:definition>06111 - Disclosure - Segment Information (Details Textual)</link:definition>
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        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>06101 - Disclosure - Commitments and Contingencies (Details Textual)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/EquityDetailsTextual" id="EquityDetailsTextual">
        <link:definition>06081 - Disclosure - Equity (Details Textual)</link:definition>
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        <link:definition>06053 - Disclosure - Goodwill and Other Intangible Assets (Details Textual)</link:definition>
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        <link:definition>06052 - Disclosure - Goodwill and Other Intangible Assets (Details 2)</link:definition>
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        <link:definition>06051 - Disclosure - Goodwill and Other Intangible Assets (Details 1)</link:definition>
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        <link:definition>0511 - Disclosure - Segment Information (Tables)</link:definition>
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      <link:roleType roleURI="http://quantaservices.com/role/SegmentInformationDetails" id="SegmentInformationDetails">
        <link:definition>0611 - Disclosure - Segment Information (Details)</link:definition>
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        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>0610 - Disclosure - Commitments and Contingencies (Details)</link:definition>
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        <link:definition>0510 - Disclosure - Commitments and Contingencies (Tables)</link:definition>
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        <link:definition>00 - Document - Document and Entity Information</link:definition>
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        <link:definition>0508 - Disclosure - Equity (Tables)</link:definition>
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        <link:definition>0608 - Disclosure - Equity (Details)</link:definition>
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        <link:definition>0506 - Disclosure - Per Share Information (Tables)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/PerShareInformationDetails" id="PerShareInformationDetails">
        <link:definition>0606 - Disclosure - Per Share Information (Details)</link:definition>
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        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>0605 - Disclosure - Goodwill and Other Intangible Assets (Details)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>0505 - Disclosure - Goodwill and Other Intangible Assets (Tables)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/SummaryOfSignificantAccountingPoliciesPolicies" id="SummaryOfSignificantAccountingPoliciesPolicies">
        <link:definition>0402 - Disclosure - Summary of Significant Accounting Policies (Policies)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/SummaryOfSignificantAccountingPoliciesTables" id="SummaryOfSignificantAccountingPoliciesTables">
        <link:definition>0502 - Disclosure - Summary of Significant Accounting Policies (Tables)</link:definition>
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        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/SummaryOfSignificantAccountingPoliciesDetails" id="SummaryOfSignificantAccountingPoliciesDetails">
        <link:definition>0602 - Disclosure - Summary of Significant Accounting Policies (Details)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/BusinessAndOrganizationDetails" id="BusinessAndOrganizationDetails">
        <link:definition>0601 - Disclosure - Business and Organization (Details)</link:definition>
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        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://quantaservices.com/role/StockholdersEquity" id="StockholdersEquity">
        <link:definition>0208 - Disclosure - Equity</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/DebtObligations" id="DebtObligations">
        <link:definition>0207 - Disclosure - Debt Obligations</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/ChangesInAccountingPrinciplesAndNewAccountingPronouncements" id="ChangesInAccountingPrinciplesAndNewAccountingPronouncements">
        <link:definition>0203 - Disclosure - New Accounting Pronouncements</link:definition>
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        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/SummaryOfSignificantAccountingPolicies" id="SummaryOfSignificantAccountingPolicies">
        <link:definition>0202 - Disclosure - Summary of Significant Accounting Policies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>0111 - Statement - Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/CommitmentsAndContingencies" id="CommitmentsAndContingencies">
        <link:definition>0210 - Disclosure - Commitments and Contingencies</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>0211 - Disclosure - Segment Information</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>0206 - Disclosure - Per Share Information</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/GoodwillAndOtherIntangibleAssets" id="GoodwillAndOtherIntangibleAssets">
        <link:definition>0205 - Disclosure - Goodwill and Other Intangible Assets</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/BusinessAndOrganization" id="BusinessAndOrganization">
        <link:definition>0201 - Disclosure - Business and Organization</link:definition>
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        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/StatementsOfCashFlows" id="StatementsOfCashFlows">
        <link:definition>0130 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/StatementsOfOperations" id="StatementsOfOperations">
        <link:definition>0120 - Statement - Condensed Consolidated Statements of Operations (Unaudited)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>0110 - Statement - Condensed Consolidated Balance Sheets (Unaudited)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
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  <element id="pwr_MinimumFutureLicensingRevenuesThereafter" name="MinimumFutureLicensingRevenuesThereafter" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_ElectricPowerDivisionMember" name="ElectricPowerDivisionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NaturalGasAndPipelineDivisionMember" name="NaturalGasAndPipelineDivisionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_TelecommunicationsDivisionMember" name="TelecommunicationsDivisionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_GoodwillAndOtherIntangibleAssetsTextualAbstract" name="GoodwillAndOtherIntangibleAssetsTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_FutureAmortizationExpenseRemainderOfCurrentPeriod" name="FutureAmortizationExpenseRemainderOfCurrentPeriod" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_PerShareInformationTextualAbstract" name="PerShareInformationTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_DebtObligationsTextualAbstract" name="DebtObligationsTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_ReductionInCompanyMaximumFundedDebtAndMaximumSeniorDebtByAllCashAndCashEquivalentsInExcessOfAmount" name="ReductionInCompanyMaximumFundedDebtAndMaximumSeniorDebtByAllCashAndCashEquivalentsInExcessOfAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_NonCashCompensationExpenseAndRelatedTaxBenefitsAbstract" name="NonCashCompensationExpenseAndRelatedTaxBenefitsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_EquityTextualAbstract" name="EquityTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_MinimumFutureLicensingRevenuesRemainderOfCurrentYear" name="MinimumFutureLicensingRevenuesRemainderOfCurrentYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_FutureAmortizationExpenseInThirdFullFiscalYear" name="FutureAmortizationExpenseInThirdFullFiscalYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_FutureAmortizationExpenseInFifthFullFiscalYearAndThereafter" name="FutureAmortizationExpenseInFifthFullFiscalYearAndThereafter" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_ActualTaxBenefitExpenseFromVestedRestrictedStock" name="ActualTaxBenefitExpenseFromVestedRestrictedStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_ActualTaxBenefitExpenseRelatedToStockBasedCompensationExpense" name="ActualTaxBenefitExpenseRelatedToStockBasedCompensationExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_CommitmentsAndContingenciesTextualAbstract" name="CommitmentsAndContingenciesTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_EmployersLiabilityInsuranceClaimsDeductible" name="EmployersLiabilityInsuranceClaimsDeductible" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_WorkersCompensationInsuranceClaimsDeductible" name="WorkersCompensationInsuranceClaimsDeductible" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_EstimatedCostToCompleteBondedProjects" name="EstimatedCostToCompleteBondedProjects" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_SegmentInformationTextualAbstract" name="SegmentInformationTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_ElectricPowerSegmentMember" name="ElectricPowerSegmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NaturalGasAndPipelineSegmentMember" name="NaturalGasAndPipelineSegmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_TelecommunicationsSegmentMember" name="TelecommunicationsSegmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_FiberOpticLicensingSegmentMember" name="FiberOpticLicensingSegmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_CorporateAndNonAllocatedCostsMember" name="CorporateAndNonAllocatedCostsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_GeneralLiabilityInsuranceClaimsDeductible" name="GeneralLiabilityInsuranceClaimsDeductible" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_AutoLiabilityInsuranceClaimsDeductible" name="AutoLiabilityInsuranceClaimsDeductible" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_ExchangeableSharesOfSubsidiaryMember" name="ExchangeableSharesOfSubsidiaryMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_FiniteLivedIntangibleAssetsForeignCurrencyAdjustments" name="FiniteLivedIntangibleAssetsForeignCurrencyAdjustments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_PaymentOfFireSuppressionCosts" name="PaymentOfFireSuppressionCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_OtherDamages" name="OtherDamages" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_FutureAmortizationExpenseInSecondFullFiscalYear" name="FutureAmortizationExpenseInSecondFullFiscalYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_FutureAmortizationExpenseInFourthFullFiscalYear" name="FutureAmortizationExpenseInFourthFullFiscalYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_LongTermInsuranceClaims" name="LongTermInsuranceClaims" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_InterimCondensedConsolidatedFinancialInformationPolicyTextBlock" name="InterimCondensedConsolidatedFinancialInformationPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NonCashPortionOfLossOnEarlyExtinguishmentOfDebt" name="NonCashPortionOfLossOnEarlyExtinguishmentOfDebt" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_RedemptionPremiumOnConvertibleSubordinatedNotes" name="RedemptionPremiumOnConvertibleSubordinatedNotes" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_LongTermIncentivePlansTextualAbstract" name="LongTermIncentivePlansTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_BaseRateInExcessOfFederalFundsRate" name="BaseRateInExcessOfFederalFundsRate" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_CrossDefaultProvisions" name="CrossDefaultProvisions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_CommonStockAvailableForAwardsPursuantToPlan" name="CommonStockAvailableForAwardsPursuantToPlan" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueRemainderOfCurrentYear" name="OperatingLeasesFutureMinimumPaymentsDueRemainderOfCurrentYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueInFirstFullYear" name="OperatingLeasesFutureMinimumPaymentsDueInFirstFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueInSecondFullYear" name="OperatingLeasesFutureMinimumPaymentsDueInSecondFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueInThirdFullYear" name="OperatingLeasesFutureMinimumPaymentsDueInThirdFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_HealthCareDeductible" name="HealthCareDeductible" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueInFourthFullYear" name="OperatingLeasesFutureMinimumPaymentsDueInFourthFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_NewAccountingPronouncementsNotYetAdoptedPolicyTextBlock" name="NewAccountingPronouncementsNotYetAdoptedPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_RedemptionPriceAsPercentageOfPrincipalAmountOfConvertibleSubordinatedNotes" name="RedemptionPriceAsPercentageOfPrincipalAmountOfConvertibleSubordinatedNotes" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_MinimumFutureLicensingRevenuesInFirstFullYear" name="MinimumFutureLicensingRevenuesInFirstFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_MinimumFutureLicensingRevenuesInThirdFullYear" name="MinimumFutureLicensingRevenuesInThirdFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_MinimumFutureLicensingRevenuesInSecondFullYear" name="MinimumFutureLicensingRevenuesInSecondFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_MinimumFutureLicensingRevenuesInFourthFullYear" name="MinimumFutureLicensingRevenuesInFourthFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_FutureAmortizationExpenseInFirstFullFiscalYear" name="FutureAmortizationExpenseInFirstFullFiscalYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_TaxBenefitRelatedToStockBasedCompensationExpense" name="TaxBenefitRelatedToStockBasedCompensationExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueAfterFourthFullYearForInterimPeriodsOrAfterFiveFullYearsForYearEndReportingPeriods" name="OperatingLeasesFutureMinimumPaymentsDueAfterFourthFullYearForInterimPeriodsOrAfterFiveFullYearsForYearEndReportingPeriods" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_NumberOfLawsuitsRelatedToWildfireLitigation" name="NumberOfLawsuitsRelatedToWildfireLitigation" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_AdditionalBusinessAndOrganizationTextualAbstract" name="AdditionalBusinessAndOrganizationTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_AdditionalLongTermIncentivePlansTextualAbstract" name="AdditionalLongTermIncentivePlansTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_CommonStockWithheldForSettlementOfEmployeeTaxLiabilitiesMember" name="CommonStockWithheldForSettlementOfEmployeeTaxLiabilitiesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_CommonStockRepurchasedUnderRepurchasePlanMember" name="CommonStockRepurchasedUnderRepurchasePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_EquityAdditionalTextualAbstract" name="EquityAdditionalTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_OutstandingPerformanceBonds" name="OutstandingPerformanceBonds" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_NumberOfInsurersParticipatingUnderReservationOfRights" name="NumberOfInsurersParticipatingUnderReservationOfRights" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_FiberOpticLicensingTermsMinimumInYears" name="FiberOpticLicensingTermsMinimumInYears" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_FiberOpticLicensingTermsMaximumInYears" name="FiberOpticLicensingTermsMaximumInYears" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NumberOfSharesOfCommonStockReceivedForEachExchangeableShare" name="NumberOfSharesOfCommonStockReceivedForEachExchangeableShare" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_DamagesCausedToAcreageDueToWildfire" name="DamagesCausedToAcreageDueToWildfire" type="num:areaItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_DamagesCausedToHomesAndStructuresDueToWildfire" name="DamagesCausedToHomesAndStructuresDueToWildfire" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_AllegedDeathsCausedByWildfire" name="AllegedDeathsCausedByWildfire" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_AllegedNumberOfPersonalInjuriesCausedByWildfire" name="AllegedNumberOfPersonalInjuriesCausedByWildfire" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_LandDamagedDueToWildfireInAcres" name="LandDamagedDueToWildfireInAcres" type="num:areaItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NumberOfInsurersClaimingCoverageDoesNotExist" name="NumberOfInsurersClaimingCoverageDoesNotExist" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_DecreaseInFairValueOfReportingUnitsConsideredForImpairmentCalculation" name="DecreaseInFairValueOfReportingUnitsConsideredForImpairmentCalculation" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_AgreedAmountOfLoanToIndirectParentOfLlc" name="AgreedAmountOfLoanToIndirectParentOfLlc" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_ValardConstructionLpMember" name="ValardConstructionLpMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_AdditionToIndefiniteLivedIntangibleAssets" name="AdditionToIndefiniteLivedIntangibleAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_InvestmentsInAffiliatesAndOtherEntitiesPolicyTextBlock" name="InvestmentsInAffiliatesAndOtherEntitiesPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_ScheduleOfNewAccountingPronouncementAndChangesInAccountingPrinciplesPolicyTextBlock" name="ScheduleOfNewAccountingPronouncementAndChangesInAccountingPrinciplesPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_CommonStockRepurchasedRelatedToRepurchasePlanPolicyTextBlock" name="CommonStockRepurchasedRelatedToRepurchasePlanPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <element id="pwr_FiniteLivedIntangibleAssetsFutureAmortizationExpenseForNextFiveYearsAndThereafter" name="FiniteLivedIntangibleAssetsFutureAmortizationExpenseForNextFiveYearsAndThereafter" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_MinimumNumberOfSharesThatCanBeExchangedByExchangeableShareholdersUnlessNumberOfRemainingExchangeableSharesRegisteredInNameOfHolderIsLess" name="MinimumNumberOfSharesThatCanBeExchangedByExchangeableShareholdersUnlessNumberOfRemainingExchangeableSharesRegisteredInNameOfHolderIsLess" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NewAccountingPronouncementsTextBlock" name="NewAccountingPronouncementsTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_LimitedVoteCommonStockMember" name="LimitedVoteCommonStockMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_FractionOfVoteCommonStockholdersWereAllowedOnAllMattersOtherThanElectionOfBoard" name="FractionOfVoteCommonStockholdersWereAllowedOnAllMattersOtherThanElectionOfBoard" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_NumberOfCommonStockSharesReceivedForEachShareOfCommonStockConverted" name="NumberOfCommonStockSharesReceivedForEachShareOfCommonStockConverted" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_LiabilitiesUnderCompensationPlan" name="LiabilitiesUnderCompensationPlan" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_NumberOfPreferredStockIssuedToVotingTrust" name="NumberOfPreferredStockIssuedToVotingTrust" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_CoeGroupMember" name="CoeGroupMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_AcquisitionsTextualAbstract" name="AcquisitionsTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_PercentageOfCapitalStockOfDirectForeignSubsidiariesRequiredToSecureCreditAgreement" name="PercentageOfCapitalStockOfDirectForeignSubsidiariesRequiredToSecureCreditAgreement" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NumberOfCustomersRepresentingTenPercentOrMoreOfConsolidatedRevenues" name="NumberOfCustomersRepresentingTenPercentOrMoreOfConsolidatedRevenues" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_PercentOfConsolidatedRevenuesForOneMajorCustomer" name="PercentOfConsolidatedRevenuesForOneMajorCustomer" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_PercentOfConsolidatedRevenuesForSecondMajorCustomer" name="PercentOfConsolidatedRevenuesForSecondMajorCustomer" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_BusinessAcquisitionProFormaEarningsPerShareAbstract" name="BusinessAcquisitionProFormaEarningsPerShareAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_BusinessAcquisitionsProFormaSellingGeneralAndAdministrativeExpenses" name="BusinessAcquisitionsProFormaSellingGeneralAndAdministrativeExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_BusinessAcquisitionsProFormaAmortizationOfIntangibleAssets" name="BusinessAcquisitionsProFormaAmortizationOfIntangibleAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_SwingLineLoansMember" name="SwingLineLoansMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_DebtObligationsAdditionalTextualAbstract" name="DebtObligationsAdditionalTextualAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_PerformanceLetterOfCreditMember" name="PerformanceLetterOfCreditMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_RateInExcessOfEurocurrencyRate" name="RateInExcessOfEurocurrencyRate" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_ConsiderationAbstract" name="ConsiderationAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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</schema>
