NORMAN, Okla. (AP) - TCU came up with its biggest upset in 45 years, stifling Heisman hopeful Adrian Peterson and beating No. 7 Oklahoma 17-10 Saturday.

Tye Gunn threw for 226 yards and a touchdown as the Horned Frogs (1-0) handed the stunned Sooners (0-1) their first home loss since 2001 and the only loss in September under Bob Stoops.

The decisive score came on a 2-yard run by Robert Merrill with 11:56 left after the Horned Frogs took advantage of a fumble by Oklahoma backup quarterback Rhett Bomar . Bomar, who lost a quarterback competition to Paul Thompson but did well enough in Stoops' eyes to earn playing time, fumbled while retreating and trying to spin away from Jamison Newby . David Hawthorne picked up the ball at the TCU 17, and Merrill took an option pitch from Gunn and scored untouched four plays later.

The Sooners had one final chance with 2:05 left, but Thompson - who replaced 2003 Heisman winner Jason White this season - fumbled on a fourth down play with 1:03 left and the Horned Frogs recovered and ran out the clock.

Oklahoma fans quickly filed out while TCU players gathered by the band for the fight song amid the cheers of two sections of purple-clad Frogs fans in the south stands.

The Horned Frogs last beat a team so highly ranked on Oct. 29, 1960, when they defeated No. 7 Baylor 14-6. TCU also upset No. 2 Texas 14-9 on Nov. 14, 1959.

Peterson had 63 yards on 22 carries and left the game briefly late in the third quarter with an apparent injury to his right ankle. He returned early in the fourth quarter after having the ankle heavily taped, but lost yardage on three of his five carries.

But Peterson was ineffective long before the injury. He had only 5 yards on eight first-half carries and gained 7 yards on a pair of receptions.

He briefly showed the running ability that made him the Heisman runner-up last year on the opening drive of the second half. He ran six times for 43 yards and went untouched on an 11-yard touchdown run around the right end to bring the Sooners within 10-7. Garrett Hartley tied the game with a 21-yard field goal five plays after Peterson was hurt.

The Horned Frogs started two of their first three drives inside the Oklahoma 5, but were finally able to overcome the bad field position on their fourth drive. TCU got the ball at the Oklahoma 16 - its best field position to that point - and Gunn, showing off the accuracy that has earned him the top completion percentage in TCU history, marched the Horned Frogs down the field for an early 7-0 lead. He was 5-for-6 on an 11-play scoring drive that featured a 32-yard reverse by wide receiver Donald Massey .

On third-and-12 from the 16, Gunn eluded the grasp of a diving Dusty Dvoracek and fired to Derek Moore as he raced across the field. Moore took the pass, turned toward the end zone and rammed his way over safety Darien Williams for the score.

After a three-and-out by the Sooners, Gunn hit running back Lonta Hobbs , who went in motion before the snap, for a 41-yard gain down the left sideline to set up a 25-yard field goal by Peter LoCoco .

The Sooners, meanwhile, had trouble sustaining drives with Thompson at the helm and Peterson scuffling. Thompson was noticeably off target several times, including on the opening play of the game. After faking a handoff to Peterson, Thompson overthrew Travis Wilson as he streaked wide open on a post pattern down the left hash. Wilson laid out to try to make the catch, but it still sailed over his outstretched arms.

Thompson finished 11-for-26 for 109 yards with one interception.