Oklahoma State rallied from 14 points down midway through the fourth quarter to tie Oklahoma, then beat the Sooners 38-35 in overtime in Bedlam football on Saturday at Owen Field in Norman.
The win makes OSU bowl eligible for the ninth straight year, and gives OU their most losses in a season since 2009.
The Sooners got the ball first and used exclusively running plays to march 75 yards in seven plays, with Samaje Perine scoring on a four-yard run around the left side to put OU on top 7-0 with 12:15 to play in the first quarter.
Perine had runs of 15 and 27 on the drive, while Alex Ross had a gain of 17.
Oklahoma State responded with an impressive drive to answer the Sooner score, going 77 yards in nine plays to tie it.
Mason Rudolph, the OSU freshman making just his second start at quarterback, threw to James Washington for a gain of 26, then to Jeremy Seaton for 29.
The Cowboys capped the drive on a one-yard touchdown run by Desmond Roland to tie the game 7-7 with 8:32 to play in the first quarter.
Both teams were forced to punt on their next possession, then OU moved the ball as the first quarter was ending.
Cody Thomas, OU's freshman quarterback making his third straight start in place of the injured Trevor Knight, passed to Blake Bell for a gain of 55 to get into field goal range as the quarter ended.
The Sooners converted a third down to start the second quarter, then were aided by two pass interference penalties against OSU in the end zone.
Oklahoma took advantage of the second penalty, with Aaron Ripkowksi scoring from a yard out to put the Sooners up 14-7 with 11:57 to play in the first half.\
The touchdown capped a 13-play, 85-yard drive.
Ripkowski was honored with the Don Key Award before the game.
The award goes to the the OU senior for all-around excellence in the classroom and on the field.
Oklahoma State answered with their own score, with Rudolph passing to Brandon Sheperd for a 39-yard touchdown to tie the game at 14 with 9:24 to play in the first half.
The Sooners responded by going to the ground game again, marching 55 yards in five plays, all of them runs, with Perine scoring from nine yards out to give OU the lead again, 21-14, with 6:53 to play in the second quarter.
The drive was aided by a 32-yard kick return from Alex Ross to the OU 45, and a facemask penalty on OSU's Ryan Simmons.
Oklahoma forced OSU to punt after just three downs, then marched to another score.
Perine picked up 42 yards on a run around the right side, then Thomas passed to Bell, who made a one-handed catch for a gain of 12 to the Cowboy 7.
Three plays later, Thomas passed in the left flat to Ripkowski, who caught the ball at the 4-yard line, then dragged OSU cornerback Kevin Peterson and a couple other defenders into the end zone for the touchdown to make it 28-14 with 3:09 to play in the first half.
Thomas was 10 of 17 passing for 120 yards.
Oklahoma led 28-14 at halftime.
The Sooners held OSU to just one first down on the opening possession of the second half, then Oklahoma began to chew up ground and time on their first possession of the half.
OU had a 14-play drive going when Perine fumbled on 3rd and 1, with Larry Stephens recovering at the OSU 29-yard line.
It was the Cowboys' first fumble recovery of the season.
Perine was injured on the play and had a bag of ice wrapped around his lower left leg.
He walked to the lockerroom late in the third quarter and did not return.
Perine finished with 151 yards on 26 carries and two touchdowns.
Oklahoma State finally broke the game's scoring drought by marching 79 yards in 7 plays.
Tyreek Hill ran for a gain of 32, and Desmond Roland capped the drive with a 3-yard touchdown run to cut the Sooner lead to 28-21 with 11:56 to play in the fourth quarter.
Roland rushed for 68 yards on 18 carries and had two scores.
With their most important possession of the game, OU responded with an 82-yard drive in 9 plays.
Keith Ford gained 56 yards on a run up the middle, reaching the OSU 27-yard line.
The Sooners then finished the drive on Ripkowski's third touchdown of the day, a one-yard plunge to make it 35-21 Sooners with 7:54 to play in the fourth quarter.
The two teams exchanged punts, and then OSU cut it to a seven-point game, with Rudolph passing to Brandon Sheperd for a 43-yard touchdown to make it 35-28 Oklahoma with 4:51 to play.
Rudolph was 19 for 35, for 273 yards passing and two touchdowns.
Sheperd had 7 catches for 156 yards and Rudolph's two TD passes.
The Cowboys forced OU to punt and had a chance to tie the game, but Rudolph was intercepted by Zack Sanchez with three and a half minutes to play and it appeared the Sooners would hold on to win.
OSU's defense forced another Sooner punt with under a minute to play.
The Cowboys were called for a running into the kicker penalty on the initial punt and the down was replayed.
The replay was OSU's biggest play of the season, as Tyreek Hill returned the punt 92 yards down the left sideline to tie the game 35-35 with 45 seconds to play.
The Cowboy defense held the Sooners on the final possession and the game was headed to overtime tied at 35.
In OT, OU got the ball first but had to settle for a 44-yard field goal attempt from Michael Hunnicutt.
His attempt was wide left, and OSU got the ball only needing a field goal to win it.
Five runs by Roland set OSU up with a chip shot for Ben Grogan, and he drilled a 21-yarder to win it for the Cowboys, 38-35.
It's OSU's first win in Norman since 2001, and just their second Bedlam win in the last 12 meetings.
The victory gets the Cowboys bowl eligible with a 6-6 record as they finish 4-5 in conference play.
Oklahoma ends the regular season 8-4, 5-4 in the Big 12.