Prospectus Supplement No. 3                     Filed Pursuant to Rule 424(b)(3)
(To Prospectus dated February 12, 2004)           Registration Number 333-111738


                                  $270,000,000

                              QUANTA SERVICES, INC.

               4.50% CONVERTIBLE SUBORDINATED DEBENTURES DUE 2023
                                       AND
    THE COMMON STOCK ISSUABLE UPON CONVERSION OR REPURCHASE OF THE DEBENTURES
                        ---------------------------------

           This prospectus supplement relates to the resale by the holders of
our 4.50% Convertible Subordinated Debentures Due 2023 and the shares of our
common stock issuable upon the conversion or repurchase of the debentures.

           This prospectus supplement should be read in conjunction with, and
may not be delivered or utilized without, the prospectus dated February 12,
2004, Supplement No. 1 to such prospectus dated March 8, 2004 and Supplement No.
2 to such prospectus dated March 26, 2004. The terms of the debentures are set
forth in the prospectus.

    THIS INVESTMENT INVOLVES RISKS. SEE "RISK FACTORS" BEGINNING ON PAGE 5 OF
                                 THE PROSPECTUS.

           Neither the Securities and Exchange Commission nor any state
securities commission has approved or disapproved of these securities or
determined if the prospectus or this prospectus supplement is truthful or
complete. Any representation to the contrary is a criminal offense.

           The information in the table appearing under the heading "Selling
Security Holders" in the prospectus is amended by adding the information below
with respect to persons not previously listed in the prospectus and by
supplementing the information with respect to other persons previously listed in
the prospectus that are listed below.




                                                  PRINCIPAL AMOUNT OF        PERCENTAGE OF        SHARES OF          PERCENTAGE OF
                                                DEBENTURES BENEFICIALLY       DEBENTURES         COMMON STOCK         COMMON STOCK
NAME                                             OWNED THAT MAY BE SOLD       OUTSTANDING          OFFERED            OUTSTANDING
----                                             ----------------------       -----------          -------            -----------
                                                                                                         
Geode U.S. Convertible Arbitrage Fund(1)......    $        7,000,000             2.59%               628,592              *
Pacific Life Insurance Company(2) ............    $          500,000               *                  44,899              *



---------------------------------
* Less than one percent.

(1)   Vincent Gubitosi has voting and dispositive power over the securities held
      by this security holder. Geode U.S. Convertible Arbitrage Fund is a series
      of Geode Investors LLC, a Delaware series limited liability company. Geode
      Capital Management, LLC, a Delaware limited liability company, is the
      manger and investment manager of Geode Investors LLC. Geode Capital
      Management, LLC is a registered investment advisor and a wholly-owned
      subsidiary of Geode Capital Holdings LLC. Shares of Geode Capital Holdings
      LLC are owned primarily by officers and senior employees of Fidelity,
      including Edward C. Johnson 3d, Abigail P. Johnson, Robert L. Reynolds,
      Laura B. Cronin, Timothy Hayes, Francis V. Knox, Jr., Eric D. Rolter and
      Philip L. Bullen, and members of their families through partnerships and
      trusts for their benefit. Mr. Johnson 3d, Ms. Johnson and members of their
      families indirectly own a majority of the shares through an irrevocable
      voting trust for their benefit administered by a trustee who is not an
      interested person of Fidelity or the Johnson family.

(2)   Larry Card, Elaine Havens, Simon Lee and Rex Olson have voting and
      dispositive power over the securities held by this security holder.

                        ---------------------------------

            The date of this prospectus supplement is April 30, 2004.