Campbell was going for his second straight stunner in Norman -- the Cyclones accelerated their revival two years ago with a 38-31 win on the same field. He said he didn't regret going for two because Purdy already had passed for 282 yards and five touchdowns and rushed for 55 yards and another score.
"When I see Brock Purdy making unbelievable play after unbelievable play, I'd rather put the game in his hands because I trust him," Campbell said. "Yeah, the question if I would do it over again. Yes, in a heartbeat."
Jalen Hurts passed for 273 yards and three touchdowns and ran for 68 yards and two more scores for the Sooners (8-1, 5-1 Big 12).
"You have games like this," Oklahoma coach Lincoln Riley said. "You don't want them, especially when you have a chance to separate like we did. But if they happen, you've got to find a way to man up and find a way to win in the end. And I'm really proud of our kids, our defense, for doing that in the end."
Oklahoma extended its November winning streak to 18 games and set up a showdown at league-leading Baylor next week.
Breece Hall rushed for 110 yards for the Cyclones (5-4, 3-3).
Lamb put on a show in the second quarter. On his 62-yard touchdown reception, he caught the ball on the left sideline, then cut across to the opposite sideline. He lowered his shoulder through a defender to reach the end zone and push Oklahoma's lead to 28-7.
The Sooners seemingly took control with a 10-play, 97-yard drive in the third quarter. Brooks finished it with a 48-yard run that gave Oklahoma a 42-21 lead.
Purdy connected with Sean Shaw for a 33-yard touchdown to trim Oklahoma's lead to 42-35, then Hurts threw an interception to give Iowa State good field position and set up the final sequence.
Iowa State: All four of the Cyclones' losses are by seven or fewer points. The Cyclones are a play here and there from a special season.
Oklahoma: The Sooners barely hung on and still have questions about their defense heading into the showdown with Baylor.
There may be some room for the Sooners to move up with losses by Alabama and Penn State. Iowa State is a respected opponent, so the Sooners won't be downgraded for playing a close game.
Iowa State hosts Texas on Saturday.
Oklahoma plays at No. 11 Baylor on Saturday in a matchup that will affect the Big 12 title picture and could affect the College Football Playoff.
South Carolina QB Jake Bentley transferring to Utah
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QB Joe Burrow, QB Justin Fields, QB Jalen Hurts, DE Chase Young are finalists for Heisman Trophy
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