EVANSTON, Ill. -- Penn State sleepwalked through the first 30 minutes yesterday and trailed at halftime for the first time this season.

But the Nittany Lions got it together in the second half, ripping off 24 unanswered points to beat pesky Northwestern, 34-13, at Ryan Field.

No. 12 Penn State (8-1, 4-1 Big Ten) broke open a tight game with three touchdowns in a span of 3:40 in the fourth quarter.

Tailback Evan Royster scored on a career-long 69-yard run, wide receiver Derek Moye caught a career-long 53-yard touchdown pass and fullback-turned-tailback Brandon Beachum scored his first touchdown of the year on a 2-yard run.

Collin Wagner also kicked his second field goal in the third quarter, a 23-yarder, as the Lions rebounded from a 13-10 halftime deficit.

"It was a bit frustrating at first, but we answered the call," said quarterback Daryll Clark, who completed 22 of 31 passes for 274 yards and one touchdown. He was sacked once and ran six times for 16 yards and a score.

The victory was the fifth in a row for Penn State, which welcomes quarterback Terrelle Pryor and No. 17 Ohio State (7-2, 5-1) to Beaver Stadium Saturday.

"We're going to play a good football team," coach Joe Paterno said. "I haven't looked at enough tapes yet to know how good they are, but I'm sure they're going to be really good."

Northwestern (5-4, 2-3) suffered a major blow in the second quarter when quarterback Mike Kafka left with a leg injury with 8:15 remaining and did not return.

He completed 14 of 18 passes for 128 yards and carried eight times for 42 yards and a touchdown and he lost a fumble before departing. His replacement, Dan Persa, was 14 of 23 for 115 yards. He also had 42 yards on 14 carries.

Asked what his team changed between the halves, Paterno said: "The adjustment we made is that their quarterback got hurt."

Penn State's defense sacked Persa four times -- and Kafka twice -- and the Lions also forced two fumbles.

Kafka had given the Wildcats a 10-3 lead when he scored on a 7-yard keeper early in the second quarter.

"He got us in some situations in the first half where we were back on our heels and huffing and puffing," said outside linebacker Sean Lee, who made his first start in six games since spraining his left knee Sept. 19 against Temple. He finished with a team-high 12 tackles, including 10 solos, as the Lions improved to 7-1 on the road the past two seasons.

Clark tied the score, 10-10, with a 2-yard run at 3:39 remaining in the first half. It was the 20th rushing touchdown of his career, tying him with Michael Robinson for the most in school history among quarterbacks.

Northwestern's Stefan Demos kicked a 45-yard field goal with three seconds left to give the Wildcats a three-point halftime lead. Fifty-one seconds earlier, Penn State defensive tackle Jared Odrick blocked Demos' 37-yard try with his left hand.

The Lions held the Wildcats scoreless in the second half and limited them to just 35 offensive plays and 125 yards after surrendering 45 plays and 246 yards in the opening half.

"They didn't panic," Paterno said of his team. "I think they did a good job."

Penn State broke open a 13-13 deadlock with those three quick touchdowns in the fourth quarter.

Moye's touchdown catch was his fifth of the season and Royster had his fifth rushing touchdown. Moye, from Rochester, also finished with six catches for 123 yards and Royster added 15 carries for 118 yards.

It was Moye's third 100-yard game of the year and Royster's fourth 100-yard effort in the past five games. Penn State finished with 437 yards offense.

"I'm getting more comfortable with Daryll, not just on the field, but with being able to tell him what I see, what I feel, over on the sideline," Moye said. "His pass was perfect."

NOTES -- Defensive tackles Ollie Ogbu, Devon Still and Odrick had sacks, along with defensive ends Jerome Hayes, Eric Latimore and Kevion Latham. ... Strong safety Drew Astorino and defensive end Jack Crawford had fumble recoveries ... Ako Poti made his fourth consecutive start at right tackle, but Nerraw McCormack also saw action. ... Backup tailback Stephfon Green (ankle) made the trip but did not dress. ... Middle linebacker Nate Williams (Central Catholic) tied for the team high with seven tackles for the Wildcats, while strong safety Brad Phillips (Franklin Regional) had six. Jeravin Matthews (Canon-McMillan) had two kickoff returns for 9 yards.

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