Stanford receiver Chris Owusu was taken from Reser Stadium by ambulance on Saturday after a helmet-to-helmet hit by Oregon State's Jordan Poyer.

Owusu, who was also hit hard last weekend in No. 4 Stanford's triple-overtime victory over USC, was prone on the field for several minutes after the hit midway through the second quarter.

He gave a thumbs-up after he was loaded on to a stretcher and placed into the ambulance.

Stanford reported that Owusu had a concussion but was conscious and had a full range of motion in his extremities. He was taken to the hospital for X-rays, but later returned and was in the locker room with his teammates after the game.

"It's scary, especially when it happens to a guy it's happened to before," said Stanford quarterback Andrew Luck.

Poyer hit Owusu on the run after he caught a pass from Luck. The hit knocked the ball out of Owusu's hands, and Poyer scooped it up and ran into the end zone. Poyer was charged with a personal foul and the touchdown was called back.

Poyer said he thought the hit was shoulder to helmet, but understood by the call was made.

"It was a bang-bang play. The ref saw helmet-to-helmet contact. He's going to make that call every time," Poyer said.

Last week in the 56-48 victory over the Trojans, safety T.J. McDonald leveled Owusu with a hit to the head, drawing a personal foul penalty late in regulation. The Pac-12 suspended McDonald for the first half of Friday's night game at Colorado for the late hit.

Tests after the game did not show a concussion, but Owusu did strain his shoulder.

Owusu also suffered what Stanford coach David Shaw described as a "minor concussion" in a win at Washington State in mid-October.

Owusu was limited to seven games last year due to various injuries — including at least one concussion.

Going into the game, the senior receiver had 33 catches for 370 yards and two touchdowns this season.

He had a 33-yard run against the Beavers in the first quarter.