Grenon went 18-for-27 and was intercepted once as Laval moved to 6-0 while Montreal dropped its first game of the season to fall to 5-1.
The Rouge et Or jumped out to 14-0 lead midway through the first quarter as Grenon hit Guillaume Rioux with a 59-yard touchdown pass at 10:55 before finding Pascal Lochard for a 34-yard strike at 7:54.
Montreal got a single point early in the second, but Boris Bede kicked a 42-yard field goal at 11:33 and had a rouge of his own to make it 18-1 at the half.
Laval didn't let up in the third as Samuel Hebert returned a fumble 43 yards for a touchdown before a safety made it 27-1 at the end of three quarters.
Bede kicked his second field goal from the same distance early in the final quarter before the Carabins attempted a late rally.
Montreal scored its first touchdown of the afternoon on a 13-play, 75-yard drive, culminating in quarterback Alexandre Nadeau-Piuze's six-yard TD pass to Mikhail Davidson to make it 30-8.
Carabins kicker Charles Bauer split the uprights from 22 yards in the final minute to round out the scoring.
Nadeau-Piuze finished with 218 yards and one TD.
The two teams meet again next Saturday in Montreal.Suggest a correction