UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended December 29, 2019 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 0-19655 TETRA TECH, INC. (Exact name of registrant as specified in its charter) Delaware 95-4148514 (State or other jurisdiction ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 ____________________________________________________________________________ FORM 10-K (Mark One) | ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 | | --- | | For the Fiscal Year Ended September 29, 2019 | | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 ☐ | | For the Transition Period from to | | Commission File Number 0-19655 | | ________________________ ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2019 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 0-19655 TETRA TECH, INC. (Exact name of registrant as specified in its charter) (State or other jurisdiction of incorporation or orga ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) | ý | QUARTERLY REPORT | | PURSUANT | TO | SECTION | 13 | OR | | --- | --- | --- | --- | --- | --- | --- | --- | | | 15(d) OF THE | SECURITIES | EXCHANGE ACT OF 1934 | | | | | | | For the quarterly period ended March 31, 2019 | | | | | | | | | | | OR | | | | | | | TRANSITION | REPORT | PURSUANT | TO | SECTION | 13 | OR | | o | 15(d) OF THE | SECURITIES | EXCHANGE ACT OF 1934 | | | | | | | For the transition period f ...

o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ý QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended December 30, 2018 OR Commission File Number 0-19655 TETRA TECH, INC. (Exact name of registrant as specified in its charter) Delaware 95-4148514 (State or other jurisdiction ...