Reisner hit from 36 yards with eight seconds left on the clock. Minutes earlier he missed a 50-yarder that would have put Illinois on top.
O'Toole relieved an ineffective Wes Lunt late in the first half. O'Toole finished 18 of 25 for 157 yards and a touchdown for Illinois (5-6, 2-5 Big Ten).
Christian Hackenberg threw for an 18-yard touchdown pass to Chris Godwin to put Penn State (6-5, 2-5) up early. But struggled the rest of the day. He finished 8-16 for 93 yards and the touchdown.
Mike Dudek had 11 catches for 115 yards for Illinois.
Penn State running back Akeel Lynch carried the ball 28 times for 137 yards and a 47-yard touchdown.
