STATE COLLEGE — With his team a little stunned after giving up a 75-yard punt return for a touchdown, Penn State coach Bill O’Brien walked up and down the sideline giving players a pep talk.

After everything they’ve been through over the past year, these Nittany Lions weren’t going to be denied, even after trailing by 11 going into the fourth quarter.

Quarterback Matt McGloin had the go-ahead score on a 5-yard touchdown run with 2:37 left, one of three fourth-quarter scores for Penn State, and the Nittany Lions stormed past No. 24 Northwestern 39-28 on Saturday.

“Our staff and myself, we tried to talk to the players and get them going,” O’Brien said. “We felt like we could move the ball.”

And how.

The Nittany Lions (4-2, 2-0 Big Ten) scored three times in the final 9:49, starting with McGloin’s 6-yard touchdown pass to Allen Robinson on fourth down as the receiver dragged along the back line of the end zone. Michael Zordich had a 2-point conversion run to get Penn State within 28-25 before McGloin’s scramble for a score sent the homecoming weekend crowd into a frenzy.

“Nobody’s down. There’s no quit in that locker room,” O’Brien said. “I don’t know what’s going to happen the rest of the year, but there will be no quit in that locker room.”

The Nittany Lions then stuffed Northwestern’s last-gasp drive after Trevor Siemian’s pass for Kain Colter was tipped away on fourth down. Zordich added a 3-yard touchdown run with 1:30 left to put a punctuation mark on the wild finish.

Things looked so good for Northwestern (5-1, 1-1) after Venric Mark’s 75-yard punt return for a touchdown with 50 seconds left in the third quarter demoralized the blue-and-white faithful for a 28-17 lead.

Mark also ran for a score and finished with 72 yards on 13 carries.

The Wildcats couldn’t get to 6-0 for the first time in 50 years. Even worse for Northwestern, the loss continued a disturbing trend of second-half collapses against Penn State. The Wildcats had halftime leads the previous two years before falling to the Nittany Lions.

This year, they couldn’t hang on to an 11-point lead in the fourth quarter.

“It was tough,” safety Ibraheim Campbell said about the last 15 minutes. “We’ve just got to find a way to make a play. Guys were out there for a while.”