Exhibit 23.1 Consent of Ernst & Young LLP. We consent to the incorporation by reference of our report dated August 14, 1998, with respect to the consolidated financial statements of Matrix Service Company included in this Annual Report (Form 10-K/A) for the year ended May 31, 1998, in the following registration statements. Matrix Service Company 1990 Incentive Form S-8 File No. 33-36081 Stock Option Plan Matrix Service Company 1991 Stock Option Form S-8 File No. 333-56945 Plan, as amended Matrix Service Company 1995 Nonemployee Form S-8 File No. 333-2771 Directors' Stock Option Plan Ernst & Young LLP Tulsa, Oklahoma August 23, 1999