Tyler Petite caught his second touchdown pass from Sam Darnold with 8:28 to play, and Southern California overcame four turnovers to earn a 21-17 victory over No. 21 Colorado on Saturday.
Daniel Imatorbhebhe also caught a TD pass from Darnold, who passed for 358 yards and three scores along with two fumbles and an interception. USC (3-3, 2-2 Pac-12) shredded one of the nation's top defenses for 539 yards, but Colorado's takeaways kept an otherwise one-sided game close.
In the Buffaloes' first game as a ranked team since Nov. 7, 2005, receiver Bryce Bobo threw a 67-yard touchdown pass in the third quarter and caught a tying TD pass with 10:20 to play.
Colorado (4-2, 2-1) kicked a field goal with 4:49 left after Petite's tiebreaking score , but the Trojans coolly ran out the clock.
"All Pac-12 wins are tough, especially when you turn the ball over like we did," USC coach Clay Helton said. "We really had a ton of yards, but just a bunch of turnovers."
Justin Davis rushed for 83 yards before leaving with an ankle injury early in the second half for USC, which improved to 11-0 against Colorado in the schools' history.
The Trojans' offense picked up right where it left off last week in a 41-point performance against Arizona State, while the defense held Colorado's potent offense to 371 yards - just 127 in the first half.
Steven Montez passed for 197 yards in the freshman's third straight start. Colorado career passing leaderSefo Liufau also played briefly, but neither quarterback had sustained success against USC's improving defense.
"Today was just a testament to how much work we have left," Montez said. "It's a humbling experience to show that we weren't what we thought we are, and have so much work to do. I think it will help us in the long run. It will keep us hungry and get us focused."
Bobo threw the 67-yard touchdown pass to Phillip Lindsay on a trick play for Colorado's first points in the third quarter, and he caught a 10-yard throw from Montez to cap an 84-yard tying drive.
Darnold fumbled twice in Colorado territory, including a goal-line fumble on the opening drive. Davis also fumbled deep in Buffs territory in the second half.
Bobo shushed the USC crowd after his tying TD catch, but the Trojans got rolling on their tiebreaking drive when Darreus Rogers reached over Colorado cornerback Ahkello Witherspoon and wrestled an interception away from him for a 46-yard gain.
Colorado: The Buffaloes' return to the AP Top 25 after an 11-year absence could be over after one week after losing to a .500 opponent, but they'll have a chance to return quickly.
Colorado: The Buffaloes have plenty of work to do if they want to stay on top of the Pac-12 South standings. USC exposed deficiencies on both sides of the ball, but the Buffs' opportunistic defense kept it close and suggested that this long-downtrodden program can hang with anybody.
USC: After going 1-3 in a brutal September schedule, USC has been largely outstanding against two Pac-12 opponents in October. Coach Clay Helton surely will emphasize ball security in the upcoming week, because it's the only thing that kept this win from being a second straight blowout of a division foe.
Colorado: The Buffs are back in Boulder to host Arizona State in another key Pac-12 South showdown. The Trojans routed the Sun Devils last week.
USC: The Trojans head out for their only road game of October, traveling to Arizona. USC rallied from a big early deficit to beat the Wildcats 38-30 last season.