During a timeout with 16:31 left in the second half, Montgomery yelled at Crabbe and then shoved him in the chest.
Crabbe appeared to be agitated by the incident and had to be escorted into the tunnel by teammates Richard Solomon and Justin Cobbs.
Crabbe returned to the Bears' bench after a short while and re-entered the game. He went on to score 14 of his 23 points in the second half, leading the Golden Bears to a 76-68 win.
"Worked, didn't it?" Montgomery said after the game, according to the Associated Press. "Allen had come down twice, went to the wrong side of the court and his guy shot two 3s. I was trying to get him going. Probably overdid it a little bit but Allen's my guy. We can't win if he is not ready to play."
Montgomery later apologized for his actions in a statement.
"I have great passion for this game and tonight, I let my emotions get away from me in the heat of the moment," Montgomery wrote. "While my intent was to motivate our student-athletes, my behavior was inappropriate and I apologize for my actions."
Crabbe said that he and Montgomery have moved forward.
"An emotional game was going on at the time and I guess he was just trying to motivate me," Crabbe said. "But everything's fine. It's under the bridge. He's my coach, no hard feelings. We're just going to keep moving on."
The Bears (16-9, 8-5 Pac-12) have won five of their last six games.