Daryll Clark threw a 53-yard TD pass to Derek Moye and Evan Royster broke off a 69-yard scoring run to highlight the fourth-quarter surge that took 3 minutes, 40 seconds.
Penn State (8-1 4-1 in the Big Ten) trailed 10-3 in the second quarter when Northwestern quarterback Mike Kafka was forced out with a leg injury. And the Nittany Lions were still behind 13-10 at the half. But they blanked the Wildcats and backup QB Dan Persa in the final two quarters and gave coach Joe Paterno his 391st win.
Behind the strong running of Royster, Penn State moved in for the go-ahead touchdown early in the final quarter on a 3-yard run by Brandon Beachum that made it 20-13.