The Leafs got on the board first at 6:53 in the opening frame. Nicholas Robertson skated in on a break and beat Sam Montembeault with assists from Mark Giordano and Matt Murray.
Toronto outshot Montreal 10-8 in the first and held a 1-0 advantage after 20.
Denis Malgin doubled the Leafs lead on the power play late in the middle period. Just as it looked like the score would remain unchanged through 40, Denis Malgin took a one-touch pass from Alexander Kerfoot and made it 2-0 with 45 seconds until the break.
Toronto added one more in the final 20 off the stick of Nick Abruzzese to end it 3-0.
Arber Xhekaj notably got his first action of the preseason on Wednesday and made his presence felt, finishing the night tied with a team-leading six hits.
The Canadiens return to the ice on Thursday, when the Winnipeg Jets visit the Bell Centre.
