Missing freshman sparkplug Buddy Hield because of a broken foot, Oklahoma got a big-time boost from backup point guard Sam Grooms in the Bedlam rivalry game.

It still wasn't enough to pull out a thriller and tighten up an already close Big 12 championship race.

Marcus Smart scored 28 points, Le'Bryan Nash added a season-high 26 and No. 17 Oklahoma State beat the Sooners 84-79 in overtime Saturday to win its seventh straight game.

Grooms had a career-high 18 points and played a key role in handling the Cowboys' full-court pressure. Oklahoma overcame an early 11-point deficit and then led by 11 just after halftime, but couldn't close it out despite shooting 60 percent in the second half.

"A tough loss for sure but a really good basketball game," Oklahoma coach Lon Kruger said. "I thought guys on both teams played their hearts out. I thought it was a big-time battle from start to finish."

Smart fed Nash for a right-handed slam with 53 seconds left in overtime to put the Cowboys up 80-79, and Oklahoma couldn't come up with an answer. Markel Brown's steal led to a fast-break layup by Michael Cobbins, and Smart blocked Steven Pledger's attempt at a tying 3-pointer to give Oklahoma State the ball back with 18 seconds to go.

Smart sealed it with two free throws, and Cowboys fans stormed the court in celebration.

It was the third straight down-to-the-wire win at home for the Cowboys (19-5, 9-3), who won by two points in each of their previous two games at Gallagher-Iba Arena. It was the second straight home game to go to overtime.

"They're making me grayer and grayer by the day," Oklahoma State coach Travis Ford said, "but very proud of them."

Romero Osby had 18 points and 15 rebounds and Pledger also scored 18 for the Sooners (16-8, 7-5), who started the day one game back of first place in the Big 12, with Oklahoma State, No. 10 Kansas State and No. 14 Kansas all tied for the lead.

The Sooners beat Oklahoma State and Kansas in Norman but lost to all three on the road.

"It just shows that we can play with the better teams," Osby said. "But we've still got to go to the drawing board and correct some things. It hurts to not get a win, but it also helps to see that we can take some positives from it."

The anticipation of the game attracted the first Bedlam sellout in Stillwater in five years.

It was Oklahoma State's second sellout of the season, and the first one involved a few thousand tickets being given away after a donation from booster T. Boone Pickens. The last capacity crowd of 13,611 to come to Gallagher-Iba Arena without a free ticket promotion was in January 2011, when the school marked the 10th anniversary of a plane crash that killed 10 men associated with the basketball team.

"This rivalry is very big and it's been going for years. It definitely felt like a classic game, and we're just glad that we could come out with the victory," Smart said.

The Cowboys rallied back from the 11-point deficit to tie it at 56, then fell behind by six before Phil Forte came up with a steal at half-court and a runout layup to even the score at 69 with 2:18 remaining in regulation.

Osby and Smart each banked in a running jumper — and each missed a free throw — and Smart was able to answer another Osby jumper by hitting two free throws to tie it at 73 with 42 seconds left in regulation.

Osby missed a jumper on Oklahoma's last second-half possession, and Smart missed a 3-pointer at the buzzer to send it into overtime.

Nash also had a right-handed slam and a three-point play off a layup in the extra period to lead the Cowboys. All but three of his 26 points came in the second half, after he'd been saddled with foul trouble in the first half.

"When he's locked in, he's not bad," Ford said.

Freshman Je'lon Hornbeak, who had come off the bench for the past three games, moved back into the starting lineup to replace Hield and had 10 points. Hield had been leading the Sooners in minutes played before breaking a bone in his right foot. He'll be out four to six weeks.

"Everyone is disappointed that Buddy wasn't able to play, but that's the unfortunate nature of the game sometimes, and I thought guys responded and played their minutes really well," Kruger said.

The biggest boost came from Grooms, who hadn't had more than seven points in a game all season.

"He battled it all day long and was a big reason we were in good position there late," Kruger said. "He was attacking, he handled the pressure very well in the backcourt and played great."

Brown had 14 points for Oklahoma State, which defended its home court against the Sooners for the fourth straight time.

Forte put Oklahoma State up 19-8 just over 8 minutes in when he hit a 3-pointer from the left wing, but the Sooners responded quickly with a 9-0 run to tie it at 21.

Another run of nine straight points to finish the first half put Oklahoma up 35-27, and Hornbeak's 3-pointer made it 45-34 early in the second half.

"It's difficult walking out of here because we wanted to get this win," Grooms