Penn State scored 22 points in the fourth quarter to erase an 11-point Northwestern lead and rally for an emphatic 39-28 win, handing the Wildcats their first loss of the season.
Northwestern held a 28-17 lead at the start of the final period, but Penn State rolled through the Wildcats' tired defense for three touchdowns in the final period, including two in the final 2:37.
The Lions, who held the ball for 39:15 in the game, ran 36 plays in the fourth quarter, while Northwestern went three-and-out twice and ran just 11.
Northwestern (5-1, 1-1 Big Ten) looked to be in control after Venric Mark's 75-yard punt return for a touchdown pushed its lead to 28-17 with 50 seconds left in the third quarter.
But the fourth quarter belonged to Penn State.
The Lions (4-2, 2-0) responded to Mark's score by going 82 yards in 18 plays. Facing a fourth-and-4 at the Northwestern 6-yard line, Matt McGloin hit Allen Robinson for a touchdown. Michael Zordich ran in the two-point conversion to cut the Wildcat lead to 28-25.
After Northwestern went three-and-out, the Lions went on another long march, this one 85 yards in 15 plays. The big play again came on fourth down, this one a fourth-and-2 at the NU 19 where McGloin broke free of the pocket and extended the play before hitting Brandon Moseby-Felder for a 13-yard gain. Three plays later McGloin scored on a five-yard run for a 32-25 lead with 2:37 left.
Northwestern had a chance to cut into the lead but wound up digging itself a deeper hole. The Wildcats turned the ball over on downs after a three-yard run and three incompletions by Trevor Siemian. The last one came on fourth down, giving Penn State the ball at the NU 28.
Zordich punched in another TD with 1:30 left to close the scoring.
McGloin turned in another masterful performance against the Wildcats, competing a career-high 35 passes on 51 attempts for 282 yards and two TDs. He now has three career victories over Northwestern.
Siemian, who got the overwhelming majority of snaps at quarterback, had a subpar outing, finishing 21-of-36 for 135 yards and one score.
The fourth quarter was much like the first, as Penn State dominated play in the opening period. The Wildcats gained just 12 yards on six plays while Penn State ran 24 for 110 in the first 15 minutes.
By the time Zach Zwinak scored on a 1-yard touchdown run to push the Lions' lead to 10-0 with 9:45 left in the second quarter, Penn State enjoyed a 136-16 edge in yardage and Northwestern hadn't even registered a first down.
But the Wildcats got their big break on special teams in the second quarter, when Penn State returner Jesse Dalla Valle muffed Brandon Williams's punt and it bounced into Nick VanHoose's hands at the Lion 18-yard line.
Venric Mark scored on a 2-yard run three plays later to slice PSU's lead to 10-7.
On the Wildcats' last possession of the second quarter, Siemian completed five passes, the last of which was to a leaping Tony Jones in the back of the end zone for an 11-yard TD with :39 left. That gave the Wildcats an improbable 14-10 halftime lead.
Kain Colter, who totaled 294 yards in offense last week, was limited to just 41 against the Lions. He got one snap at quarterback in the second half and scored on a 10-yard in the third quarter. He finished with five carries for 24 yards and three catches for 17 yards.
Mark led Northwestern with 72 yards on 13 carries but didn't get a touch in the fourth quarter.
Zwinak led all rushers with 121 yards on 28 carries.