Roeland Schaftenaar tied a season high with 22 points to lead Oregon State to an 80-64 victory over Pac-10 leader California on Thursday night.
Seth Tarver added 16 points and seven assists for the Beavers (12-13, 6-7), who took an early 7-5 advantage and led the rest of the game.
Theo Robertson had 15 points and Patrick Christopher 12 for the Golden Bears (17-9, 9-5), whose lead in the conference is down to half a game.
Joe Burton's 3-pointer with 12:56 remaining capped a 9-2 Oregon State run that gave the Beavers a 52-40 lead. It was Burton's first attempt of the season from long range.
Schaftenaar's two free throws with 6:48 remaining put Oregon State ahead 65-50, and Cal got no closer than 10 points the rest of the way.
Cal's Jerome Randle, averaging 19.8 points per game, was held to six points on 2 of 9 shooting.