Northwestern was also 4 of 14 on third- and fourth-down plays, while Penn State was 15 of 28.
"That's a recipe for disaster. We're on the field way too long. We're not sustaining drives," Northwestern coach Pat Fitzgerald said. "Our recipe is exactly what they did for success. We got beat at our own game."
Yet they still were in a good spot in the third quarter after Colter had a 10-yard scoring run with 3:12 left before Mark's terrific punt return touchdown about two minutes later for a 28-17 lead.
Colter, who had nearly 300 yards of total offense last week, was held to five carriers for 24 yards and three catches for 17 yards. Robinson finished with nine receptions for 85 yards and two touchdowns.