David Pastrnak got Boston within 4-2 at 8:29 when he one-timed a pass from Marchand at the left face-off dot.
Marner made it 5-2 when he scored into an empty net with 43 seconds left.
"We've got to create our identity where we are hard to play against for 60 minutes, not 30, 20, 40, whatever it is, it has to be 60 and we weren't," Bruins coach Bruce Cassidy said. "When you get into their type of game where there's a little bit more transition, and for us, we need to play more of a puck possession in the offensive zone. There were some easy goals tonight for them -- that they worked for, don't get me wrong -- but we were soft on pucks."
Marner, Matthews, Nylander and Tavares have combined to score Toronto's past 13 goals over four games dating to the final two goals in a 5-4 win against the Detroit Red Wings on Oct. 30.
"We need those guys to produce, and they have been, and it's no coincidence it's been the start of a roll as a team since that's happened, but I really thought it was a great team effort here tonight all the way through," Maple Leafs coach Sheldon Keefe said. "We had just terrific efforts from each line, our defense, our goaltending and our special teams. This was a big win here tonight, but just like we needed to block out the noise when things were not going well, it's equally important to block out the noise now."
Campbell made 23 saves in the third period, the fourth-most in a period in Maple Leafs history.
"He's playing outstanding; he's a big part of our team," Reilly said. "When he plays well, the guys respond and it's a great feeling for our group."