Derrick Williams scored 22 points and No. 16 Arizona rode its 3-point shooting to a 78-69 victory over Oregon State in the Pac-10 tournament quarterfinals Thursday.
The top-seeded Wildcats (26-6) advanced to play fourth-seeded Southern California in Friday's semifinals at Staples Center.
Kevin Parrom added 13 points, helping the Wildcats end a three-year skid in the tourney quarterfinals. A year ago, they lost to UCLA and finished 16-15, ending the school's streak of 25 consecutive NCAA tournament appearances.
Now, Arizona remains on track to add its first league tourney title since 2002 to the regular-season championship it wrapped up last weekend. Hall of Fame coach Lute Olson, who began the school's NCAA tourney streak in 1985, was in the crowd.
Williams, the Pac-10 player of the year in his second season, was 5 of 6 on 3-pointers. Lamont Jones went 3 of 6 from beyond the arc and finished with 13 points. The senior-less Wildcats had five 3s in the second half, when they pulled away after a tight opening 20 minutes.
Jared Cunningham scored 23 points and Ahmad Starks added 17 — both one point off their career highs — for the Beavers (11-20), who split with Arizona in the regular season.
Starks sank consecutive 3s that drew the Beavers within seven midway through the second half before they lost big man Joe Burton, who had nine points and five rebounds.
Burton was assessed a flagrant foul and got ejected for elbowing Parrom in the face near the baseline with 10:25 remaining. Burton walked back to his bench claiming he got hit. Arizona fans chanted "Throw him out!" as the referees reviewed the play.
The Beavers trailed by nine when Burton left the court. Parrom scored six of the Wildcats' next nine points, with Williams adding his fifth 3-pointer to extend the lead to 70-56.
Oregon State began the game on a tear, seeking its first semifinal berth since 2005. They ran up a 22-15 lead, propelled by Cunningham's 15 points.
Arizona regrouped with 12 straight points, including consecutive 3-pointers by Jones and Williams to take its first lead. Williams hit two more 3s as the Wildcats closed the half ahead 40-37.