After a slow start, Penn State scored five unanswered against the Leopards.
The Nittany Lions' win over Illinois bumped them up two spots.
Kaytron Allen and Nick Singleton had carries in more than half of Penn State's offensive snaps.
The defensive line held the Illini to just 34 yards on the ground.
"We got challenged by [James Franklin] and we took that to heart."
Nick Singleton and Kaytron Allen were responsible for two of Penn State's three touchdowns.