FORT WORTH, Texas -- Jared Barnett threw three touchdowns to Josh Lenz, who later had a scoring toss of his own on a trick play, and Iowa State beat No. 15 TCU 37-23 on Saturday, two days after the Horned Frogs suspended quarterback Casey Pachall.
TCU (4-1, 1-1) had its 12-game winning streak, tops in major college football, snapped in its first Big 12 home game.
Barnett was 12-of-21 passing for 183 yards and ran nine times for 30 yards in his first start this season for the Cyclones (4-1, 1-1).
Iowa State won for only the third time in 33 road games against a Top 25 team since 1996. Barnett had another one of those wins, as a freshman last season at Texas Tech in his first career start.
The Frogs had won a nation-best 25 conference games in a row, the first 24 while winning the Mountain West championship each of the last three seasons. They won their Big 12 debut at Kansas three weeks ago, and hadn't lost a conference game since Nov. 6, 2008 at Utah.
Lenz had TD catches of 51 and 74 yards in the first quarter, when the Cyclones led 16-7. He capped their first drive of the second half with a 1-yard catch for a 23-10 lead.
The trickery came late in the third quarter when after taking a handoff on a reverse Lenz stopped and threw a 15-yard score to tight end Ernst Brun. That capped a 10-play drive aided by two personal foul penalties, including a late hit by standout end Stansly Maponga that wiped out a fourth-and-9 for Iowa State.
Lenz finished with five catches for 147 yards.
Steele Jantz, the senior quarterback Barnett replaced in the lineup, had one carry for 7 yards.
Dual-threat redshirt freshman Trevone Boykin took over for Pachall, the second-year starter who is suspended indefinitely after his arrest early Thursday on suspicion of driving while intoxicated.
Pachall wasn't on the sideline after coach Gary Patterson changed his initial decision to have the quarterback in uniform for the game without playing.
The coach said after the game that he would be meeting with TCU's chancellor Sunday to discuss what's next for Pachall, who eight months before his arrest this week admitted to police that he smoked marijuana and failed a team-administered drug test.
Boykin was 23 of 40 passing for 270 yards with one score. He had three interceptions, one on his first pass of the game before two more in the fourth quarter.
David Irving, a 6-foot-7, 280-pound defensive end, swatted at a pass by Boykin midway through the fourth quarter, then rumbled 20-yards for the final touchdown. The Frogs had one more drive after that, but Jake Knott picked off a pass near the goal line. Despite temperatures in the 50s, Boykin was dealing with leg cramps. He stayed on the ground after rolling right and throwing a 28-yard pass to Brandon Carter early in the fourth quarter.
When Boykin returned for the next series, Irving had his interception.
Jaden Oberkrom had field goals of 38, 50 and 39 yards for TCU, which lost for only the second time its last 30 home games.