The Cowboys were powerless to stop the 6-foot-8, 275-pound wrecking ball.
Gathers scored 14 of his 16 points after the break and led No. 17 Baylor to a 69-65 victory on Wednesday night.
Baylor trailed by five at halftime, but Gathers made three baskets in the first two minutes of the second half to trim Oklahoma State's lead to 34-33. The Bears pulled ahead with just under 14 minutes remaining and positioned themselves for the win late.
''We just knew we had to come out strong, and that was the first thing we did - just getting the ball inside,'' Gathers said. ''I think I scored three buckets back-to-back, and we just went to work from there.''
Gathers also had nine rebounds and made a critical free throw in the closing seconds. The preseason all-Big 12 selection had scored in single digits three of his previous five games and scored just two points Saturday against No. 1 Oklahoma.
Oklahoma State coach Travis Ford said Gathers' energy early in the second half was critical.
''That was big,'' Ford said. ''That was huge. That was huge. We were up five and started with the ball, and I don't know if he asserted himself more or anything or what happened, but we didn't obviously defend very well. I'm not real happy about that at all. That's not the start we were looking for, at all.''
It's just the third time in 20 years Baylor has swept the regular-season series with the Cowboys. It was also Baylor's third straight road win in league play - the Bears have knocked off Iowa State, Texas Tech and now, Oklahoma State.
''Nothing is easy in the Big 12,'' Prince said. ''I don't know how much we can stress that to you all. Anybody can lose on any given night, so if you don't come to play, if you don't execute a game plan, you might be taking an `L.'''
Ishmail Wainright's bucket in close gave Baylor a 66-63 lead with 32.2 seconds to play.
Olivier scored for Oklahoma State to make it a one-point game. The Cowboys fouled Prince with 16.2 seconds remaining, and he made both free throws.
Evans missed on a drive, and Gathers rebounded with 8.5 seconds left. He missed the first free throw, but made the second to put the game out of reach.
Evans had seven assists in the first half to lead an efficient attack. The Cowboys had assists on 10 of their 13 baskets before the break.
The Cowboys were outscored 42-33 after the break.
''We were kind of our own worst enemy, to an extent, and they capitalized,'' Ford said. ''Give Baylor credit - they capitalized on it.''
Evans had seven assists and no turnovers in the first half, and three assists and four turnovers in the second half. Oklahoma State committed 10 of its 16 turnovers in the second half.
Former Oklahoma State coach Eddie Sutton was courtside. He coached the Cowboys from 1990-2006 and led them to two Final Fours. The 79-year-old received a standing ovation when his presence was announced.
Gathers moved into fifth place in Big 12 history with 1,059 rebounds, ahead of Colorado's Stephane Pelle (1,053) and Iowa State's Melvin Ejim (1,051).
Baylor: The Bears won 79-62 on Jan. 5. ... Johnathan Motley fouled out with eight points and seven rebounds. ... Baylor outrebounded Oklahoma State 31-26.
Oklahoma State: The Cowboys wore special tribute jerseys on the 15-year anniversary of the plane crash that killed 10 people involved with Oklahoma State athletics. The jerseys, similar to those worn in the late 1990s and early 2000s, featured ''Cowboys'' in script lettering across the front. The 10 names were announced before the game, and a moment of silence followed.
Baylor hosts Georgia on Saturday.
Oklahoma State plays at Auburn on Saturday.