Tyrone Wallace added 12 points and seven assists for the Golden Bears. California (17-12, 7-9 Pac-12) snapped a three-game losing streak in its final home game of the season by beating a team with a winning record for just the third time since Jan. 2.
The Bears trailed 44-36 with 13 minutes remaining when they put together one of their best runs of the year. Cal scored 15 consecutive points and outscored the Beavers 24-2 over a six-minute span to take the lead for good. Mathews made a pair of 3-pointers during the run then capped it with two free throws that put the Bears up 60-46.
Malcolm Duvivier had 18 points and eight rebounds for Oregon State (17-12, 8-9).
David Kravish, one of three seniors on Cal, added 13 points, a season-high 13 rebounds and three blocked shots. The fifth-leading shot blocker in conference history, Kravish scored all but two of his points over the final nine minutes.
With two games left before the Pac-12 Tournament, the Bears still have a slim shot of getting a first-round bye but will need plenty of help.
Oregon State could have strengthened its hopes of getting a pass in the first round of the conference tournament by beating Cal. Instead, coach Wayne Tinkle's team lost for the fifth time in six games.
The Beavers were in position to do that until the Bears went on their big run.
Cal used its perimeter shooting to loosen up Oregon State's zone defense in the first half. The Bears made four 3-pointers, including three straight to begin the game, and took a 21-13 lead on Sam Singer's layup.
Cal closed the half on an 8-2 run and led 32-31 at the half.
Oregon State: The Beavers first four points came on two emphatic dunks by Gary Payton II. He finished with 12 points. Payton had a steal in his 29th consecutive game, tying his father for the second-longest streak in school history.
California: The Bears have won five straight against the Beavers. They haven't lost to Oregon State since Jan. 5, 2012.
Oregon State: Hosts Oregon on Wednesday.
California: At Arizona on Thursday.