Perry Jones III had 16 points and 11 60 win over Oklahoma State.
Pierre Jackson scored 16 points while Quincy Acy added 11 points and 12 rebounds for the Bears (21-2, 8-2 Big 12), who have won four straight since dropping two straight for their only losses of the season.
"It feels good. Every time we have played here before, we have lost," said Acy. "It's also good to get a win up here for Coach (Scott) Drew."
Brian Williams had a game-high 23 points while Keiton Page added 15 points and Le'Bryan Nash scored 11 for the Cowboys (11-12, 4-6), who have dropped five of their last seven.
"I'm very proud of the effort our team put into it," said Oklahoma State head coach Travis Ford. "We couldn't have played any harder. Our guys left it on the court. I wouldn't say we played particularly well, but we played hard."
Oklahoma State had never led the entire game, but a 10-2 run capped on a Page three-pointer with under two minutes to play gave the team its first lead of the contest, 57-56.
Acy, though, answered with an emphatic dunk and, following a missed three-ball from Page, Brady Heslip made a pair of free throws for a three-point lead.
Page then turned the ball over, with Heslip picking it up and hit another two from the line with 18.5 to play.
Markel Brown hit a three-pointer with 9.4 seconds to play to make it a 62-60 game.
Heslip then missed the first free throw, but Acy grabbed the offensive board and Anthony Jones hit his two foul shots with 2.8 seconds left to seal the win.
Baylor led by as many as 12 points in the first half, but Oklahoma State kept the game from getting out of hand and trailed, 37-29, after 20 minutes of play.
After a Nash layup tied the game at 39-all five minutes into the second half, Baylor scored the next nine points with Jackson hitting consecutive three- balls for a 48-39 lead with just over 10 minutes to play.
The Cowboys host Iowa State on Tuesday...Baylor hosts Kansas on Wednesday...Baylor has won seven of the last 11 against Oklahoma State, but still trails in the series, 51-18. The Bears took a 106-65 decision over the Cowboys in Baylor on January 14.