STILLWATER, Okla. — Third-string quarterback Brandon Weeden threw for 168 yards and two touchdowns in the second half, leading No. 12 Oklahoma State back from an 11-point deficit for a 31-28 win against Colorado on Thursday night.

With starter Zac Robinson injured and backup Alex Cate ineffective, Weeden took over in the second half and got the offense going for the Cowboys (9-2, 6-1 Big 12).

His 28-yard touchdown pass to Justin Blackmon with 8:11 remaining proved to be the winner, keeping pressure on No. 3 Texas in the Big 12 championship race. The Longhorns would have clinched the Big 12 South with an OSU loss.

Colorado got out to a 21-10 lead against the one-dimensional Cowboys before Weeden finally provided a viable passing threat.

The Buffaloes (3-8, 2-5) had one final chance to go for the win after stuffing OSU on fourth-and-short for the third time in the game with 3:14 remaining, but decided to punt after Tyler Hansen threw three straight incomplete passes. The Cowboys, the Big 12’s top rushing team, ran the final 2:45 off the clock.

Oklahoma State wore black uniforms for the first time since 1994 — a miserable 3-7-1 season — and they didn’t seem to be a good luck charm in the team’s first Thursday night home game since 1995.

Cate, who had attempted only five passes in his career, started in Robinson’s place but went 0-for-9 with an interception in the first half — and it could have been worse. Colorado players had chances for at least two more picks, but let the ball slip through their hands.

Weeden, a 26-year-old, came on in relief. When he completed back-to-back passes on OSU’s third drive of the third quarter, the crowd of 50,080 let out Bronx cheers.

Two plays later, Toston finished that drive with a 45-yard touchdown run through a huge hole on the right side of the line to cut the deficit to 21-17.

Colorado had a chance to stretch its lead, but Aric Goodman’s 50-yard field goal try caromed off the right upright and coach Dan Hawkins then opted to go for it on fourth-and-3 from the 29-yard line instead of sending Goodman out to try a 46-yard kick.

Oklahoma State came right back on its next possession to take the lead on Toston’s 47-yard touchdown catch.

Brian Lockridge answered with a 98-yard return for a touchdown on the ensuing kickoff to put the Buffaloes back ahead with 11:11 remaining, but Weeden responded with two big completions on third-and-long before finding Blackmon in the end zone as he scrambled to the right.

It was only the second win for OSU against Colorado in the teams’ last eight meetings in Stillwater. Both teams ended up playing switcheroo at quarterback, with Cate getting a 7-0 head start when Perrish Cox brought back Matt DiLallo’s first punt 67 yards for a score.

OSU’s defense then sacked Hansen on back-to-back plays to force a three-and-out, but Toston took a handoff from Cate on the Cowboys’ first offensive snap and fumbled for the first time in 287 carries — a span of more than two years since he’d been benched for fumble problems in September 2007.

Hansen capitalized with a 5-yard touchdown pass to Scotty McKnight before leaving briefly with a thumb injury. Cody Hawkins, the former Buffaloes starter and the coach’s son, replaced him and threw a 5-yard score to Riar Geer to put Colorado up 14-10 at halftime.