PULLMAN, Wash. -- Oregon survived 33 minutes without its leading scorer.

Junior forward Dillon Brooks, a preseason All-American, was ejected in the opening minutes, but No. 15 Oregon went on to an 85-66 win over Washington State Saturday night at Beasley Coliseum.

"It was a little shocking," Oregon guard Dylan Ennis said. "You don't normally have your best player out so early in the game, but we are deep. I am happy we came out with the win."

Center Chris Boucher scored a career-high 29 points on 11-for-15 shooting, including 6-for-9 on 3-pointers. Boucher scored 18 points in the second half as Oregon outscored the Cougars 48-29.

"We played without Dillon early in the year and the results were not good, so I was a little concerned about that," Oregon coach Dana Altman said. "I thought in the second half, our guys responded well. I was pleased with Chris."

Ennis added 17 points and forward Jordan Bell scored 11 as Oregon (15-2, 4-0) won its 13th straight game to remain unbeaten in Pac-12 play. Brooks, who was averaging 14.3 points per game, was ejected with 13:20 left in the first half after he appeared to kick Cougars forward Josh Hawkinson in the groin.

Hawkinson said he felt the kick was intentional, but Altman said he had not yet seen a replay when he met the media. Brooks was not available for interviews after the game.

Guard Ike Iroegbu led Washington State (9-6, 2-1) with 12 points while guard Charles Callison had 11 points and four assists as the Cougars dropped their first conference game.

"It was obviously a big game for us and we came in with high energy early in the game," Callison said. "In the second half, our energy level went below them and they took advantage of that."

The game was tied 37-37 at halftime and the second half started off back and forth as Ennis drilled a jumper and added a basket to put the Ducks up 45-43.

Ennis added a 3-pointer to put Oregon ahead 50-48 and forward Roman Sorkin added a 3-pointer as well. Hawkinson scored for Washington State before Bell converted a three-point play and Ennis added a 3-pointer to put the Ducks ahead 59-50.

Boucher hit a 3-pointer and later added another to stretch the lead to 69-56.

"We kind of woke up in the second half and played our game," Bell said.

Brooks opened the game with a 3-pointer for Oregon and Ennis converted from beyond the arc as Oregon took an 8-2 lead before Washington State scored seven points in a row. Center Conor Clifford scored and guard Malachi Flynn hit a 3-pointer before Charles Callison scored to put the Cougars ahead 9-8.

Brooks scored four points in a row as Oregon went ahead 12-11 before he was ejected.

Hawkinson made two free throws to put Washington State ahead 18-15 before Ennis scored to tie the game. Iroegbu and Hawkinson each scored as the Cougars took a 22-18 lead.

Guard Payton Pritchard scored for Oregon and Boucher tied the game 22-22 before guard Viont'e Daniels and Flynn hit back-to-back 3-pointers to put WSU ahead 28-22.

Center Kavell Bigby-Williams made two free throws for Oregon and Boucher hit a 3-pointer to cut WSU's lead to 28-27. Iroegbu and Daniels each hit two free throws as WSU went up 32-27 before Boucher converted a three-point play to get Oregon within 32-30.

Iroegbu scored to put WSU ahead 35-31 before Bigby-Williams scored four straight points to tie the game 35-35 before the two teams went to halftime tied 37-37.

NOTES: Oregon F Dillon Brooks scored seven points to move into 22nd place in school history with 1,241 points. ... Oregon is 4-0 in conference play for the first time since starting 7-0 in 2012-13. ... Oregon's 13-game winning streak matches its longest since the 2013-14 season. ... The Ducks have won 11 of their past 12 against the Cougars. ... Washington State fell to 5-13 against Oregon when the Ducks are in the AP Top 25.