Torey Krug had a goal and an assist, and Patrice Bergeron, David Pastrnak and Tim Schaller scored for the Bruins (31-11-8), who are 16-1-4 in their past 21 games. Rask made 23 saves.
\[WATCH: All Maple Leafs vs. Bruins highlights\]
"Toronto, when we played them last year, earlier this year, they were really skating. I thought we outskated them tonight," Bruins coach Bruce Cassidy said. "At least that's how I saw it. ... I liked the way we skated. We were winning pucks and we're killing plays in the neutral zone, getting back and re-attacking them. I thought that was the difference in the game, us being able to sustain that transition game where we were back in their end and eventually wear them down."
Mitchell Marner scored, and Frederik Andersen made 26 saves for the Maple Leafs (30-19-5), who had won their past six games against Boston, two this season.
"If you don't have everyone on deck and you're not ready to go, you're not going to win very often," Toronto coach Mike Babcock said. "So I thought we've done a good job of that of late, and I didn't think we got that tonight. Just didn't have enough players in there, and when the game was there after one [period] and you hadn't been great, it's time for pushback. We didn't have a pushback."
Bergeron scored from the slot at 4:29 of the first period for a 1-0 lead after a back pass from Danton Heinen.