Joseph Young scored 25 points, Dwayne Benjamin had 18 points and 10 rebounds, and
Elgin Cook added 17 points for the Ducks (21-8, 11-5 Pac-12).
Oregon made only four baskets over the final 11 minutes but countered that by going 10 of 11 from the free throw line down the stretch following a frenetic first half.
Young, the Pac-12's leading scorer, got the Ducks going early while Benjamin had 14 of his points in the second half.
The win keeps the Oregon in third place and strengthened its bid for a first-round bye in the postseason conference tournament.
Jabari Bird scored 22 points with six rebounds for California (16-12, 6-9).
Oregon hadn't defeated California since Feb. 9, 2008 and had dropped 12 straight before handing the Bears their third consecutive loss.
Young put on another impressive scoring display in the first half when he repeatedly scorched the Bears from the perimeter.
The Pac-12's leading scorer had 17 points before halftime, including a pair of 3-pointers that helped stake Oregon to a 39-35 lead. He missed a chance to extend the lead just before the buzzer when David Kravish blocked Young's layup attempt with two seconds remaining.
Bird, who struggled as a highly touted freshman in 2013, nearly matched Young and kept the Bears close with 16 points in the first half.