Cal (18-14) turned a close game into a rout with an impressive shooting display, making 14 of 15 shots spanning halftime to build a 17-point lead. Jordan Mathews added 19 points for the Bears.
The eight-seeded Bears shot 58.5% overall and made eight of 12 from three-point range to earn a spot in Thursday's quarterfinals against No. 5 and top-seeded Arizona.
"We established David in the post," Cal Coach Cuonzo Martin said. "I thought that set the tone for us offensively. If we're able to do that, then our perimeter guys could play."
Washington State (13-18), the tournament's No. 9 seeding, struggled defensively and failed to make a three-point shot until late in the second half.
Ike Iroegbu led the Cougars with 17 points. Leading scorer DaVonte' Lacy was held to nine points on four-for-11 shooting and struggled with emotions on the bench after his final game.
To me, part of the emotion you saw was a young man who loved his teammates, who loved his college experience, and therefore it was very difficult to see that come to an end," Cougars Coach Ernie Kent said of Lacy.
Colorado (15-16) traded shots with Beavers in an entertaining first half before stretching its lead in the second half behind Booker and Scott. Booker made three three-pointers during a key run midway through the second half and nine of 10 free throws overall.
Tre'Shaun Fletcher added 12 points for 10th-seeded Colorado, which moves on to face second-seeded Oregon in Thursday's quarterfinals.
No. 7-seeded Oregon State (17-14) had a hard time containing Booker and the Buffaloes in the second half, allowing them to make 13 of 23 shots.
Gary Payton II and Malcolm Duvivier had 17 points each and Olaf Schaftenaar added 16 for the Beavers.