Mike Cobbins made a key block in the closing seconds of overtime, leading to Markel Brown's fastbreak layup with less than a second remaining to lift No. 22 Oklahoma State over Baylor, 69-67, on Wednesday.
Brown finished with 13 points and five rebounds, while Marcus Smart contributed 14 points, eight rebounds and seven assists for the Cowboys (16-5, 6-3 Big 12), who have won four straight.
"We're glad we won. I told our guys when it's this time of year, you take them any way you can get them," Oklahoma State coach Travis Ford said. "When you're not making shots, and we were not making shots, you have to tough it out. We did that with our defense and rebounding. I was very happy with our rebounding tonight."
Pierre Jackson scored a game-high 24 points to go along with eight assists for Baylor (14-8, 5-4), but he also committed 11 of the Bears' 16 turnovers.
Cory Jefferson had 18 points and 11 rebounds in Baylor's third consecutive loss.
Oklahoma State held a 24-22 edge entering the second half, but Brady Heslip connected on a pair of 3-pointers during an opening 10-4 spurt to hand Baylor a 32-28 advantage.
The Cowboys, however, answered with a 12-2 push to regain a 40-34 lead following Brown's reverse alley-oop dunk with 13:44 left in regulation.
Jefferson put a brief end to the run with an alley-oop at the other end before Oklahoma State scored the next eight points to open up a 48-36 lead.
The Cowboys' lead later stretched as high as 14 points before Jackson made a pair of 3-pointers and Heslip added another triple during a 17-3 trek by Baylor to tie the game at 57-57 with just under two minutes to play.
Oklahoma State quickly went back on top with Smart's driving layup at the other end, and after Brown later missed a potential game-sealing 3-pointer with less than 30 seconds to play, Jackson was fouled while driving towards the net and sank both free throws with 6.5 seconds showing to tie the game at 59-59.
Brown's contested three from the left wing as time expired rimmed out to force overtime.
Jackson opened the extra period with a pair of 3-pointers around a Smart triple to hand the Bears a 65-62 advantage, but Oklahoma State scored five of the next seven points to knot the score at 67-67 with Phil Forte's 3-pointer from the top of the key with a little over a minute left.
After Jackson was forced out of bounds after taking some contact on the baseline on Baylor's ensuing possession, Smart came up empty on a layup attempt from under the rim to keep it a tie game with time winding down.
A.J. Walton then grabbed a short pass under the rim and seemed to have an easy lay-in to put Baylor on top, but Cobbins stuffed his attempt from in close and Brown grabbed the loose ball.
He immediately raced down the court and finished with a finger roll that fell through the net with 0.2 seconds showing for the deciding basket.
"I'm proud of how the guys fought back and gave us a chance to win," Baylor coach Scott Drew said. "Credit Oklahoma State for making a big block and having enough court awareness to get a shot at the other end."
Points were at a premium over the opening minutes of action as Baylor held a 9-3 lead following Deuce Bello's jumper just past the eight-minute mark of the first half.
The Cowboys then found some offensive rhythm with an 8-2 spurt to knot the game at 11-11, but the Bears responded with the game's next eight points to regain a 19-11 advantage with 5:42 remaining in the opening 20 minutes.
Oklahoma State then closed out the first half with a 13-3 run to take a 24-22 edge into the break.
Baylor shot just 33.3 percent in the first half, including a 1-for-9 mark from three-point range, while the Cowboys were held to just 30 percent from the floor and failed to connect on nine attempts from beyond the arc in the first half.
Oklahoma State improved to 52-19 against Baylor, including a 25-4 mark in Stillwater ... The Cowboys improved to 2-0 in overtime this season, while Baylor fell to 1-1 ... Oklahoma State shot 36.1 percent from the floor and 3- for-21 from three-point range ... The Bears connected on 41.9 percent of their shots and went 8-for-27 from beyond the arc.