The Spartans (1-0) overmatched their first-ever opponent from the Football Championship Subdivision, formerly known as Division I-AA.
Montana State (0-1) has lost four straight against Football Bowl Subdivision opponents since upsetting Colorado in 2006.
Cousins and Nichol are competing to replace Brian Hoyer, now a backup quarterback for the NFL's New England Patriots. Cousins got the start Saturday and completed 10 of 17 passes for 183 yards.
Nichol played most of the second quarter and started the second half. He finished 9 of 18 for 135 yards.
Blair White had nine catches for 162 yards and two TDs for Michigan State.
Montana State struggled to move the ball against an aggressive, swarming Michigan State defense led by linebacker Greg Jones with 14 tackles. The Bobcats finished with just 160 yards of offense compared to 493 yards for Michigan State.
Michigan State rolled to a 28-0 halftime lead with both its quarterbacks playing key roles.
Cousins was 0-for-2 passing on his first series as Michigan State's starting quarterback. But he settled down quickly and gave the Spartans a 7-0 lead midway through the first quarter with a 29-yard touchdown strike to a wide-open B.J. Cunningham.
Cousins found Blair White for a 15-yard TD on Michigan State's next drive, putting Montana State in a 14-0 hole.
Nichol took over and promptly led the Spartans on another scoring drive to go up 21-0 midway through the second quarter. The drive was capped with a 26-yard TD toss to Dion Sims.
Nichol rolled right and connected on a 3-yard TD pass to Brian Linthicum putting Michigan State ahead 28-0 at the half.
Michigan State kicker Brett Swenson made two field goals to increase the lead to 34-0 midway through the third quarter.
Montana State's best drive of the game came late in the third quarter, ending with a field goal by Jason Cunningham.
Montana State will receive at least $650,000 for traveling to East Lansing, enough to pay nearly a third of its annual football budget.
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