The Beavers moved out to a 12-7 lead while the Bruins struggled with turnovers and missed shots.
Then UCLA took over for good and sent Oregon State to a 74-64 defeat on Thursday night, its 23rd loss in its last 24 games on the Bruins' home court.
"The effort was good, but the execution is what has to get better," Beavers coach Craig Robinson said. "These guys got used to winning and now they have lost four in a row. And they're mad. That's good. I want them to be mad. I want them to be mad enough to play better."
Roberto Nelson scored 17 points and Joe Burton added 12 points for the Beavers (10-7, 0-4 Pac-12). They lost for the fifth time in their last six games.
"We showed some toughness, but we need to improve on our transition defense," said Devon Collier, who had nine points and seven rebounds. "We also need to limit our turnovers (17). UCLA scored on a lot of turnovers."
Shabazz Muhammad scored 21 points, Kyle Anderson and Travis Wear had 17 each for the Bruins (15-3, 5-0), whose 10th straight victory equaled their longest winning streak since 2008-09.
Ahead by 11 points at halftime, UCLA ran off 11 straight early in the second half to take a 48-28 lead.
Muhammad had a three-point play, Wear and Jordan Adams had baskets and Anderson scored four straight points during the run that put the Beavers in a double-digit deficit the rest of the game.
Oregon State got to 58-48 during an 8-0 run capped by Nelson's 3-pointer. But Muhammad answered with a 3-pointer to key a 7-0 spurt and extend UCLA's lead to 65-48.
The Beavers were held under their 75.7-point scoring average. They are one of two Pac-12 teams with five players averaging double figures, but only three players reached that mark in the game.
The Bruins settled down and outscored the Beavers 20-7 to take a 27-19 lead. Muhammad and Norman Powell hit consecutive 3-pointers, while Travis Wear had six points in the spurt.
Anderson and Muhammad combined to score UCLA's final eight points of the first half, extending its lead to 37-26.
Oregon State forward Eric Moreland and guard Victor Robbins were suspended for the game after violating team rules. They will be available to play at Southern California on Saturday.
"They will be fresh and we will need those fresh bodies," said Robinson, who will leave his team after Saturday's game to fly to Washington, D.C., to attend the inauguration of his brother-in-law, President Barack Obama. He will be back in time for the Beavers' home game against Washington on Wednesday.
Former UCLA star Jamaal Wilkes had his No. 52 jersey retired at halftime, with former Bruins stars Bill Walton, Kareem Abdul-Jabbar and Mike Warren on hand. He helped lead the Bruins to NCAA championships in 1972 and 1973 under coach John Wooden. Wilkes had his jersey retired by the Los Angeles Lakers last month, and he was inducted into the Naismith Memorial Basketball Hall of Fame last year.