But not this season.
For the first time, the Cardinal isn't entering the conference tournament as regular-season champion.
Stanford had won or shared every regular-season title since 2001. But Oregon State won it this season and is the favorite as play begins at KeyArena in Seattle.
UCLA (12-17) opens against Arizona (10-19) on Thursday at 2 p.m., with the winner playing Stanford (21-9) in a quarterfinal game Friday. USC (15-14) plays Colorado (13-16) on Thursday at 6 p.m., with the winner facing Oregon State (26-3) in a quarterfinal game. Oregon (13-16) plays Washington State (16-13) and Utah (9-20) plays Washington (22-8) in other first-round games Thursday. Arizona State (26-4) and California (21-8) have the other first-round byes.
The winner of Sunday's championship game earns the conference's automatic bid to the NCAA tournament.
Oregon State made quick rise to the top of the conference. The Beavers finished tied for 10th in Pac-12 play two seasons ago with a 4-14 record, which was consistent with their history.
From 1986-87, when the Pac-12 women's conference was formed, to 2012-13, Oregon State had a .352 winning percentage and three winning records during conference play.
Oregon State made a big jump last season, finishing tied for second during the regular season and advancing to the Pac-12 tournament title game, where the Beavers lost to USC. Oregon State advanced to the NCAA field, where it defeated Middle Tennessee for its first NCAA tournament win since 1995.
Stanford has won or shared 23 of the 28 regular-season titles and won 10 of 13 conference tournament championships. Stanford's run of seven consecutive conference tournament championships ended last season with a loss to USC in a semifinal game. This season, the Cardinal tied for third in the regular-season standings.
Oregon State's program began to change when Scott Rueck was hired as coach in 2010. Rueck had coached 14 seasons at George Fox, winning an NCAA Division III national title in 2009. Oregon State has won at least 20 games in three of his five seasons.
Also Thursday, the West Coast Conference women's basketball tournament opens at Orleans Arena in Las Vegas.
Pepperdine (8-21) and Loyola Marymount (6-23) meet in a first-round game at noon, with the winner facing Santa Clara (10-17) or Portland (4-25).
Gonzaga (23-6) is the top-seeded team in the tournament.