Cousins threw a 33-yarder to Cunningham in the third quarter and hit him again on a juggling 29-yard TD pass with 5:17 left to complete a 93-yard drive. It was the 62nd career touchdown pass for Cousins, breaking the school record held by Jeff Smoker (61).
Northwestern (6-6, 3-5) had its four-game winning streak snapped in the regular-season finale and now hopes for a bowl bid. The Wildcats closed to 24-17 early in the final quarter on Dan Persa's 12-yard TD pass to Demetrius Fields, set up by a clutch fourth-down pass from Persa to Jeremy Ebert.
The Wildcats got the ball back at the MSU 47, but a holding penalty and Jerel Worthy's sack of Persa forced a punt and then MSU went on its long, game-clinching drive.
Martin sprinted in on his 57-yard punt return with 34 seconds left in the half as Michigan State scored two touchdowns in the final 1:40 of the second quarter and took a 17-3 lead at the intermission.