SECURITIES AND EXCHANGE COMMISSION
                                WASHINGTON, D.C. 20549

                                     SCHEDULE 13G

               INFORMATION STATEMENT PURSUANT TO RULES 13d-1 AND 13d-2
                    UNDER THE SECURITIES AND EXCHANGE ACT OF 1934
                                 (Amendment No. 2 )*


                                  Matrix Service Co.
- --------------------------------------------------------------------------------
                                   (Name of Issuer)


                                     Common Stock
- --------------------------------------------------------------------------------
                            (Title of Class of Securities)


                                      576853105
- --------------------------------------------------------------------------------
                                    (CUSIP Number)



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

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).


                           (Continued on following page(s))
                                  Page 1 of 8 Pages



CUSIP No. 576853105                   13G               Page  2  of  8  Pages
- ----------------------                               ---------------------------

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

              The TCW Group, Inc.
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                        (a)  / /
                                                                        (b)  /X/
- --------------------------------------------------------------------------------
3   SEC USE ONLY

- --------------------------------------------------------------------------------
4   CITIZENSHIP OR PLACE OF ORGANIZATION

         Nevada corporation
- --------------------------------------------------------------------------------
           NUMBER OF              5    SOLE VOTING POWER
           SHARES                                                     567,700
        BENEFICIALLY              ---------------------------------------------
          OWNED BY                6    SHARED VOTING POWER
            EACH                                                          -0-
           REPORTING              ---------------------------------------------
           PERSON                 7    SOLE DISPOSITIVE POWER
            WITH                                                      567,700
                                  ---------------------------------------------
                                  8    SHARED DISPOSITIVE POWER
                                                                          -0-
- --------------------------------------------------------------------------------
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
                                                                      567,700
- --------------------------------------------------------------------------------
10  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES
    CERTAIN SHARES*
                                                                          / /
- --------------------------------------------------------------------------------
11  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
     6.1% (see response to Item 4)
- --------------------------------------------------------------------------------
12  TYPE OF REPORTING PERSON*
                                        HC/CO
- --------------------------------------------------------------------------------



                    *SEE INSTRUCTIONS BEFORE FILLING OUT!



CUSIP No. 576853105                   13G               Page  3  of  8  Pages
- ----------------------                               ---------------------------

- --------------------------------------------------------------------------------
1   NAME OF REPORTING PERSON
    S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

              Robert Day
- --------------------------------------------------------------------------------
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                        (a)  / /
                                                                        (b)  /X/
- --------------------------------------------------------------------------------
3   SEC USE ONLY

- --------------------------------------------------------------------------------
4   CITIZENSHIP OR PLACE OF ORGANIZATION

         United States Citizen
- --------------------------------------------------------------------------------
           NUMBER OF              5    SOLE VOTING POWER
           SHARES                                                     567,700
        BENEFICIALLY              ---------------------------------------------
          OWNED BY                6    SHARED VOTING POWER
            EACH                                                          -0-
           REPORTING              ---------------------------------------------
           PERSON                 7    SOLE DISPOSITIVE POWER
            WITH                                                      567,700
                                  ---------------------------------------------
                                  8    SHARED DISPOSITIVE POWER
                                                                          -0-
- --------------------------------------------------------------------------------
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
                                                                      567,700
- --------------------------------------------------------------------------------
10  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES
    CERTAIN SHARES*
                                                                          / /
- --------------------------------------------------------------------------------
11  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
     6.1% (see response to Item 4)
- --------------------------------------------------------------------------------
12  TYPE OF REPORTING PERSON*7
                                        HC/IN
- --------------------------------------------------------------------------------



                    *SEE INSTRUCTIONS BEFORE FILLING OUT!



                                                               Page 4 of 8 Pages

Item 1(a).    Name of Issuer:

              Matrix Service Co.

Item 1(b).    Address of Issuer's Principal Executive Offices:

              10701 E. Ute St.
              Tulsa, OK 74116-1517

Item 2(a).    Name of Persons Filing:
Item 2(b).    Address of Principal Business Office:
Item 2(c).    Citizenship:

              The TCW Group, Inc.
              865 South Figueroa Street
              Los Angeles, CA 90017
              (Nevada Corporation)

              Robert Day
              200 Park Avenue, Suite 2200
              New York, New York 10166
              (United States Citizen)

Item 2(d).    Title of Class of Securities:

              Common Stock

Item 2(e).    CUSIP Number:

              576853105



                                                               Page 5 of 8 Pages

Item 3.       If this statement is filed pursuant to Rules 13d-1(b), or
              13d-2(b), check whether the person filing is a:

         (a)  [ ]  Broker or Dealer registered under Section 15 of the Act:

                        Not applicable

         (b)  [ ]  Bank as defined in Section 3(a)(6) of the Act:

                        Not applicable

         (c)  [ ]  Insurance Company as defined in Section 3(a)(19) of the Act:

                        Not applicable

         (d)  [ ]  Investment Company registered under Section 8 of the
                   Investment Company Act:

                        Not applicable

         (e)  [ ]  Investment Adviser registered under Section 203 of the
                   Investment Advisers Act of 1940:

                        Not applicable

         (f)  [ ]  Employee Benefit Plan, Pension Fund which is subject to the
                   provisions of the Employee Retirement Income Security Act of
                   1974 or Endowment Fund (SEE 13d-1(b)(1)(ii)(F)):

                        Not applicable

         (g)  [X]  Parent Holding Company, in accordance with Rule
                   13d-1(b)(ii)(G) (SEE Item 7):

                        The TCW Group, Inc.
                        Robert Day (individual who may be deemed to control The
                             TCW Group, Inc. and other holders of the Common
                             Stock of the issuer)

         (h)  [ ]  Group, in accordance with Rule 13d-1(b)(1)(ii)(H):

                        Not applicable.



                                                               Page 6 of 8 Pages

Item 4.       Ownership **

         THE TCW GROUP, INC.

              (a)  Amount beneficially owned: 567,700

              (b)  Percent of class: 6.1%

              (c)  Number of shares as to which such person has:

                   (i)   Sole power to vote or to direct the vote:
                           567,700

                   (ii)  Shared power to vote or to direct the vote:   none.

                   (iii) Sole power to dispose or direct the disposition of:
                           567,700
  
                   (iv)  Shared power to dispose or to direct the disposition
                   of:  none.

         ROBERT DAY

              (a)  Amount beneficially owned: 567,700

              (b)  Percent of class: 6.1%

              (c)  Number of shares as to which such person has:

                   (i)   Sole power to vote or to direct the vote:
                           567,700

                   (ii)  Shared power to vote or to direct the vote: none.

                   (iii) Sole power to dispose or direct the disposition of:
                           567,700

                   (iv)  Shared power to dispose or to direct the disposition
                   of:  none.

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

** The filing of this Schedule 13G shall not be construed as an admission that
the reporting person or any of its affiliates is, for the purposes of Section
13(d) or 13(g) of the Securities Exchange Act of 1934, the beneficial owner of
any securities covered by this Schedule 13G.  In addition, the filing of this
Schedule 13G shall not be construed as an admission that the reporting person or
any of its affiliates is the beneficial owner of any securities covered by this
Schedule 13G for any other purposes than Section 13(d) of the Securities
Exchange Act of 1934.



                                                               Page 7 of 8 Pages

Item 5.       Ownership of Five Percent or Less of a Class.

                   Not applicable.

Item 6.       Ownership of More than Five Percent on Behalf of Another Person.

              Various persons other than as described in Item 4 have the right
              to receive or the power to direct the receipt of dividends from,
              or the proceeds from the sale of, the Common Stock of Matrix
              Service Co.

Item 7.       Identification and Classification of the Subsidiary Which
              Acquired the Security Being Reported on by the Parent Holding
              Company.

              SEE Exhibit A.

Item 8.       Identification and Classification of Members of the Group.

              Not applicable. SEE Exhibits A and B.

Item 9.       Notice of Dissolution of Group.

              Not applicable.

Item 10.      Certification.

         Because this statement is filed pursuant to Rule 13d-1(b), the
         following certification is included:


         By signing below I certify that, to the best of my knowledge and
         belief, the securities referred to above were acquired in the ordinary
         course of business and were not acquired for the purpose of and do not
         have the effect of changing or influencing the control of the issuer
         of such securities and were not acquired in connection with or as a
         participant in any transaction having such purpose or effect.




                                                               Page 8 of 8 Pages

                                      SIGNATURE


              After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this statement is true,
complete and correct.


Dated this 12th day of February, 1997.



                                       The TCW Group, Inc.


                                       By:  /s/ Mohan V. Phansalkar
                                            -----------------------
                                            Mohan V. Phansalkar
                                            Authorized Signatory


                                       Robert Day


                                       By:  /s/ Mohan V. Phansalkar
                                            -----------------------
                                            Mohan V. Phansalkar
                                            Under Power of Attorney dated
                                            January 30, 1996, attached as
                                            Exhibit C hereto.




                                      EXHIBIT A


                   RELEVANT SUBSIDIARIES OF PARENT HOLDING COMPANY

PART A: TCW ENTITIES

PARENT HOLDING COMPANY:

              The TCW Group, Inc.

              Robert Day (an individual who may be deemed to control The TCW
              Group, Inc.)


RELEVANT SUBSIDIARIES THAT ARE PERSONS DESCRIBED IN RULE 13d-1(b):

         (i)   Trust Company of the West, a California corporation and a bank
         as defined in Section 3(a)(6) of the Securities Exchange Act of 1934.

Note:         No Common Stock of Matrix Service Co. is held directly by The TCW
              Group, Inc.  Other than the indirect holdings of The TCW Group,
              Inc. no Common Stock of Matrix Service Co. is held directly or
              indirectly by Robert Day, an individual who may be deemed to
              control The TCW Group, Inc.

PART B: NON TCW ENTITIES

PARENT HOLDING COMPANY:

              Robert Day (an individual who may be deemed to control the
              holders described below which are not subsidiaries of The TCW
              Group, Inc.)

RELEVANT SUBSIDIARIES THAT ARE PERSONS DESCRIBED IN RULE 13d-1(b):

              Oakmont Corporation, a California corporation and an Investment
              Adviser registered under Section 203 of the Investment Advisers
              Act of 1940.

              Cypress International Partners Limited, a British Virgin Islands
              corporation and an Investment Adviser registered under Section
              203 of the Investment Advisers Act of 1940.


                                         A-1




                                      EXHIBIT B

                                JOINT FILING AGREEMENT


         The undersigned acknowledge and agree that the foregoing statement on
Schedule 13G is filed on behalf of each of the undersigned and that all
subsequent amendments to this statement on Schedule 13G shall be filed on behalf
of each of the undersigned without the necessity of filing additional joint
acquisition statements.  The undersigned acknowledge that each shall be
responsible for the timely filing of such amendments, and for the completeness
and accuracy of the information concerning him or it contained therein, but
shall not be responsible for the completeness and accuracy of the information
concerning the other, except to the extent that he or it knows or has reason to
believe that such information is accurate.


Dated: February 12, 1997

                                       The TCW Group, Inc.


                                       By:  /s/ Mohan V. Phansalkar
                                            -----------------------
                                            Mohan V. Phansalkar
                                            Authorized Signatory


                                       Robert Day


                                       By:  /s/ Mohan V. Phansalkar
                                            -----------------------
                                            Mohan V. Phansalkar
                                            Under Power of Attorney dated
                                            January 30, 1996, attached as
                                            Exhibit C hereto.


                                         B-1