NORMAN, Okla. -- With Dede Westbrook out, Samaje Perine and Joe Mixon took over for Oklahoma.

Perine provided the bruising physicality while Mixon flashed the speed, helping the No. 9 Sooners to a 38-20 win over No. 10 Oklahoma State in front of 87,527 at Gaylord Family-Oklahoma Memorial Stadium.

After missing three games with a hamstring injury late in the year, Perine had been steadily ramping up his production before breaking out with a 239-yard performance Saturday.

It was Perine's fifth career 200-yard game and moved him to within 83 yards of breaking Billy Sims' Sooners' career rushing record.

He and Mixon combined for 338 yards and two touchdowns on the ground, and Mixon added another score on a pass to give the Sooners (10-2, 9-0 Big 12) the first perfect record in Big 12 play since Texas in 2009.

"That was a big deal to the players through the week," Sooners coach Bob Stoops said. "We've never had a chance to hoist a Big 12 championship trophy on our home field. Now did we need any more motivation? I don't think so."

For most of the year, Westbrook had been the Sooners' big-play man, and he added some of that early with a 69-yard touchdown reception. But when he was knocked out with an injury before halftime, it was Oklahoma's ground game that took over.

The game was tied at 17 at halftime before Perine started asserting himself.

On the first play of the half, the junior broke away for a 66-yard gain. Six plays later, Perine carried it in himself to put Oklahoma ahead for good.

"Always waiting for the floodgates to open," Sooners quarterback Baker Mayfield said. "They always do with this offense."

After the game, Mayfield announced that he would return for his senior season.

Mayfield threw for 288 yards and three touchdowns while his Oklahoma State counterpart, Mason Rudolph, threw for 186 yards without a score through the air.

"We couldn't get a very good grasp of the ball," Cowboys coach Mike Gundy said of the rainy conditions. "It wasn't a really good day for us to have an opportunity to throw it down the field."

Mixon's two second-half touchdowns helped keep the Sooners in front, with his 79-yard touchdown run with just less than 10 minutes remaining all but sealing the game.

"I think it's pretty clear what happened," Gundy said. "One of the things that I had concerns with coming in was them getting big plays, and that's what happened. Unfortunately, we played pretty good, in fact maintained some quality drives and had some defensive stands, but they big-played us."

Barring something unexpected in the College Football Playoff rankings, the Sooners appear to be headed to the Sugar Bowl for the second time in four seasons. Oklahoma State (9-3, 7-2) is likely headed to the Alamo Bowl to play a Pac-12 opponent.

Oklahoma's defense, which had struggled to slow down offenses for much of the season, came through after halftime as well.

The Cowboys ran for 186 yards in the first half but managed just 31 yards on the ground after the break.

Sooners linebacker Ogbonnia Okoronkwo was also a disruptive force throughout, twice sacking Rudolph and getting close several more times.

Westbrook had four catches for 111 yards before his second-quarter injury.

Going over the middle while attempting to make a catch, Westbrook took a hard hit from Oklahoma State free safety Jordan Sterns and remained motionless on the ground for several moments.

Eventually, he was able to walk off the field under his own power.

He remained dressed out on the sidelines for the remainder of the game but did not return.

Oklahoma State had life early in the fourth quarter when Perine was forced to the locker room with an injury in the fourth quarter after fumbling.

But after driving 61 yards in 3:40, Oklahoma State's Ben Grogan missed a field goal to keep the margin at 11. Mixon then exploded for his big touchdown run on the next play to put the game away.

"What a run," Stoops said. "He hit another gear and great job at the end adjusting, cutting back. Separating that way was huge."

NOTES: Oklahoma RB Joe Mixon became the fourth Sooners player to gain more than 2,000 all-purpose yards in a season. DeMarco Murray (twice), Quentin Griffin and Greg Pruitt were the others. ... A Southwest Airlines Boeing 737 did the pregame flyover, honoring Southwest employee and former Sooners punter Mike Winchester, who was shot and killed Nov. 15 at Oklahoma City's Will Rogers World Airport. ... With his 32-yard run late in the first quarter, Oklahoma State RB Justice Hill broke the 1,000-yard barrier, becoming the first Cowboys freshman to top that mark. ... Oklahoma CB Parrish Cobb, who hadn't played since the loss to Ohio State in September and was expected to redshirt, came into the game late in the third quarter after Jordan Parker was injured.