Stanford (22-9) led by 12 midway through the second half before a 15-3 run by the Bruins pulled them even at 56-56 with 4:59 left on Kacy Swain's jumper. Stanford scored the next five points, but UCLA staged one last rally, pulling within 63-62 with 21.9 seconds left on Jordin Canada's driving layup following a turnover by the Cardinal.
UCLA nearly forced another turnover, but Stanford's Bonnie Samuelson hit a pair of free throws with 14 seconds left to push the Cardinal lead back to three. Paulina Hersler's three-point attempt in the final seconds for UCLA appeared to be partially deflected and fell short.
Canada led the sixth-seeded Bruins (13-18) with 15 points, Kari Korver added 12 and Swain scored 10.
Stanford, the third seed, will play No. 9-ranked second seed Arizona State in the semifinals tonight. The Sun Devils swept the Cardinal in the regular season.
Arizona State 67, Washington State 48: The ninth-ranked Sun Devils are thrilled to be sticking around for the weekend and another chance to improve their case for a higher seed in the NCAA tournament after they failed to win a game in the last two Pac-12 Conference tournaments.
Sophie Brunner scored eight of her 14 points in the first five minutes of the second half, Quinn Dornsauder added 12 points off the bench and Arizona State pulled away in the second half to beat Washington State in the quarterfinals of the Pac-12 tournament.
Promise Amukamara scored 11 points for the Sun Devils, helping make up for leading scorer Katie Hempen being held to four points. Arizona State, the No. 2 seed, overcame a sluggish first half for its sixth straight victory.
"It's just nice to stay here more than a day. We haven't built much history at this tournament in Seattle yet, so very proud of our team," Arizona State Coach Charli Turner Thorne said. "We've been a little slow starting lately offensively, and then we've been able to get it going in the second half this last week or so."
The Sun Devils (27-4) led only 19-16 at halftime but opened the second half on a 25-11 run. Sixteen of the 25 points during the run were scored inside the point with Brunner and Kelsey Moos doing most of the damage as Arizona State couldn't be slowed on the interior.
Moos and Brunner scored 16 of the 25 points during the Sun Devils' run, capped by Elisha Davis' three-pointer with 11:47 left for a 17-point lead. The Cougars got no closer than 11.
Tia Presley led Washington State (17-14) with 16 points and Lia Galdeira added 12, but the Cougars were just one of 14 on three-point attempts.
Colorado 68, Oregon State 65: Lexy Kresl scored 19 points, Jamee Swan picked up 11 of her 18 in the second half and Colorado stunned No. 8 Oregon State in the Pac-12 Conference tournament quarterfinals.
Colorado (15-16) watched the regular-season champion Beavers erase a seven-point deficit and take a 60-59 lead with 4:21 remaining on Ruth Hamblin's three-point play.
But the Buffaloes scored the next eight points and held Oregon State scoreless for more than four minutes. Swan gave Colorado the lead for good with her jumper in the lane with 2:38 left and Kresl's backdoor cut for a layup with 1:05 left pushed the lead to five.
Oregon State (26-4) lost for the second time in three games and is now left to wonder what the late slide will do to its NCAA tournament seeding. Hamblin led the Beavers with 14 points but Sydney Wiese and Ali Gibson combined to shoot six of 26 from the field.
Jen Reese added all 13 of her points in the second half as the Buffaloes beat a ranked team for the first time this season.
California 69, Washington 53: Brittany Boyd scored 20 points, and Mercedes Jefflo added 16 points as the Golden Bears (22-8) beat the Huskies (23-9). California will now play Colorado in the Pac-12 Conference tournament's semifinals.