Quarterback Steve Smith passed for three touchdowns and ran for two in a 35-point second period as the Big Ten-leading Wolverines won in Evanston, Ill.
Smith scored on runs of 11 and one yards and passed for touchdowns of 34 and 29 yards to all-America Anthony Carter and of 12 yards to Craig Dunaway after Mike Mallory had recovered a Northwestern fumble.
"Steve Smith can do more than any guy who takes the ball from center in this league," said Coach Bo Schembechler. "No one runs like him."
The Wolverines (5-2, 5-0) won their fourth in a row. Northwestern (2-6, 1-5) had won two straight at home.
The Wolverines scored on all six possessions in the first half. Carter ran back the opening kickoff 33 yards to the Michigan 40 and Smith completed three passes in a 60-yard drive ended by Lawrence Ricks' one-yard plunge.
Northwestern then went 85 yards but was stopped when Keith Bostic intercepted Sandy Schwab's pass at the Michigan two and returned to the 16. Smith took over for the rest of the half as the Wolverines piled up a 42-0 lead.
"We didn't make any mistakes in the first half on offense," said Schembechler, who took out most of his starters at the half. "I debated at halftime and with four big games coming up, I didn't want to take any chances."
Smith gained 71 yards in nine carries in his half and completed 10 of 12 passes for 203 yards. Carter's two touchdowns gave him 36, breaking his tie for a school record at 34 with Rick Leach.
Northwestern's Jon Harvey caught 17 passes to break the Big Ten record of 15 set by teammate Todd Jenkins last week. Schwab set a Big Ten record with 45 completions in 71 attempts, the latter an NCAA mark. He finished with 436 yards passing, a school record.