Chiney Ogwumike had a double-double by halftime, finished with 23 points and 21 rebounds and No. 4 Stanford remained perfect against Washington State with a 79-60 win Friday night in the Pac-12 Conference tournament quarterfinals.

The Cardinal won their 15th straight and improved to 55-0 all-time against the Cougars. They will play either No. 18 Colorado or Washington in the semifinals on Saturday night.

Ogwumike's skill on the interior overwhelmed the Cougars in the first half before getting help from her teammates in the second half as Stanford (29-2) finally pulled away. It was the second 20-20 game this season for Ogwumike, who had 27 points and 24 rebounds against Oregon.

Lia Galdeira led Washington State (11-20) with 16 points. The Cougars had coach June Daugherty back on the bench a day after she underwent emergency surgery to remove her appendix.

Sara James added 17 points — 14 in the second half — and Joslyn Tinkle scored 10 for the Cardinal. Stanford beat Washington State last Saturday in Pullman 72-50 for its 54th straight win over the Cougars. It became 55 in-a-row six days later, although it was a first-half performance the Cardinal will not be pleased about with the exception of Ogwumike. She was 6 of 7 shooting and 5 of 7 at the line and recorded a double-double within the first 13 minutes. She finished the first half with 17 points and 12 rebounds, but the rest of Stanford's lineup was a combined 6 of 20 in the first half.

Stanford led by as many as 17 only to see the Cougars cut the deficit to 31-23 on Mariah Cooks' basket with 1:45 left. Orange scored as the shot clock expired and Ogwumike's steal and driving layup just before the halftime horn gave the Cardinal a 35-23 lead at the break.

But help arrived early in the second half. James hit a pair of 3s early in the half and Ogwumike didn't score for the first 7 minutes. By the time she did, the Cardinal had stretched the lead to 19.

Washington State advanced to the quarterfinals for the second straight year and the loss was muted by the return of Daugherty to the bench. Daugherty was cleared by doctors to attend Friday's game, but sat behind the Cougars bench while her husband Mike was the lead coach for the second straight night.

That didn't stop her from getting involved. She was on the floor giving out high-fives just before the opening tip and during timeouts would join her team in the huddle. Occasionally Daugherty would linger next to her husband and give instruction as play was happening before returning to her seat.

For all the instruction given, the Cougars simply couldn't keep up with Stanford. Galdeira was limited to just four points in the first half thanks to foul trouble then was hounded by James and sometimes Ogwumike in the second half.