WACO, Texas -- Baylor quarterback Seth Russell served notice that the Bears' passing game is as potent as ever.

Russell threw for 387 yards and four touchdowns to propel No. 16 Baylor past Oklahoma State 35-24 on Saturday night at McLane Stadium.

When Oklahoma State tied the game at 21 early in the third quarter on Rennie Childs' 3-yard touchdown run, it took Russell and the Bears less than a minute to answer.

Russell responded by throwing deep to wide receiver Chris Platt for an 89-yard touchdown to give Baylor (4-0, 1-0 Big 12) the lead for good.

And while Russell was directing the offense into its usual rhythm, the Bears' defense made the key plays it needed to remain the only undefeated team in the Big 12.

Oklahoma State (2-2, 0-1) threatened to take the lead midway through the fourth quarter when it drove inside the Baylor 15. But Cowboys running back Justice Hill fumbled while stretching for extra yards and Bears nickel back Travon Blanchard recovered at the 1.

"I was really proud of the way our defense bowed their necks when they had to, made plays down the stretch," Baylor interim coach Jim Grobe said. "It seems like when our defense gets our backs against the wall, we play better. I'd just like to go ahead and spot them on the 20 and say 'let's play football.'"

The fumble recovery set up Russell for his finest drive of the season. The Baylor quarterback completed 4 of 4 passes for 104 yards. Russell finished it by hitting Platt for a 15-yard touchdown and a double-digit lead for the first time.

Oklahoma State quarterback Mason Rudolph passed for 279 yards and Hill rushed for 122 and a touchdown on 20 carries. The Cowboys gave up four turnovers to Baylor's two.

Oklahoma State also failed to score on three drives deep into Bears territory in the fourth quarter.

"When you're moving the ball and turn it over you just shoot yourself in the foot," Oklahoma State coach Mike Gundy said. "When you give up big plays when you have them backed up against the wall, then it's hard to beat a good team. It's really pretty simple."

Baylor wide receiver Ishmael Zamora, who was suspended for the first three games of this season after video surfaced of him beating a dog, made the most of his first action.

When Russell's pass bounced off the hands of Bears receiver Lynx Hawthorne early in the second quarter, Zamora raced under the deflected ball and took it the rest of the way for a 38-yard touchdown.

The score put Baylor ahead 14-7, but Zamora wasn't finished.

After Oklahoma State tied it at 14, Russell threw over the top of the Cowboys, this time intentionally to Zamora, who hauled in the catch inside the 5 and fought his way into the end zone for another 38-yard score.

"We knew Ish had potential," Grobe said. "I don't think he caught a lot of balls last year, but the coaches saw in spring practice, and I could see in our summer practices, that he had talent."

Oklahoma State took advantage of a Baylor mistake to tie the game in the first quarter.

Bears punt returner Tony Nicholson backpedaled to catch a punt inside his own 5. Oklahoma State's Ashton Lampkin knocked the ball loose from Nicholson's grasp and Tanner Morgan recovered for the Cowboys.

Oklahoma State needed one play to convert the recovery into points as Hill ran 5 yards for the score.

Rudolph sparked the Cowboys' second scoring drive of the first half as he connected on 5 of 6 passes for 49 yards. The Cowboys quarterback found Jalen McCleskey for 14 yards on a third-and-12 play to set up first-and-goal from the Baylor 6.

Two plays later, Childs ran 3 yards for a touchdown to tie it at 14 with 5:32 left before halftime.

But Oklahoma State couldn't find the same kind of execution in the fourth quarter with a chance to upset Baylor at home.

"I'll tell you the same thing I told the team, 'I can pat you on the butt and tell you good job and you guys played good against a team that's ranked,'" Gundy said. "That's not the way I feel. I feel like we should have done a better job of coaching and we've got to do a better job of playing. We can win these games."

NOTES: Oklahoma State had its six-game winning streak snapped in true road games. The run, which began immediately after the Cowboys lost at Baylor in 2014, included victories over Oklahoma in 2014 and at Texas, West Virginia, Texas Tech and Iowa State last season in Big 12 play (the Cowboys also went on the road to defeat Central Michigan in 2015). ... Baylor entered the game ranked seventh nationally in total defense at 249.3 yards after wins over Northwestern State, SMU and Rice, but permitted 492 to the Cowboys. ... Lightning in the area caused a 95-minute delay early in the first quarter. Baylor had just scored on running back Terence Williams's 23-yard touchdown run with 13:22 remaining in the first quarter when game officials announced that the teams would be sent to the locker room because of a lightning strike within 10 miles of McLane Stadium.