Jakub Vrana had a goal and an assist to extend his point streak to nine games, and Braden Holtby made 31 saves for Washington (34-11-5), which leads the NHL with 73 points.
"He was great today," Vrana said. "He made some huge saves and shut it down back there."
[WATCH: All Capitals vs. Canadiens highlights]
Ovechkin, who has eight goals in his past three games, including consecutive hat tricks, served a one-game suspension for sitting out the 2020 Honda NHL All-Star Game in St. Louis on Saturday. The Capitals are 15-14-2 with him out of the lineup since 2005-06.
"Obviously it's a big goal-scoring loss for us, but we stick together as a team," Vrana said. "We still kept creating chances today, especially the fourth line. I felt like they had lots of chances, they played really good, and that was a great team win."
Carey Price made 36 saves for Montreal (22-22-7), which had won its past two games.
"I don't think they got an edge on us," Canadiens forward Ilya Kovalchuk said. "The second period was sloppy by us, I think the first and third we played really well. But that's not enough."
Jeff Petry gave the Canadiens a 1-0 lead at 1:55 of the first period. He took a pass from Tomas Tatar, cut across the crease and scored on a backhand shot.
Video: WSH@MTL: Tatar, Petry get Canadiens started early
Vrana set up Tom Wilson with a centering pass from behind the net for a power-play goal that tied it 1-1 at 18:30.
"He's playing really well," Wilson said. "He's having a great season and it's fun to be out there with him whenever you are."
Travis Boyd got credit for putting the Capitals ahead 2-1 at 2:03 of the second. His shot in the goalmouth struck Petry's skate and went over the goal line before the Montreal defenseman could stop it.
"I think we started the game out well," Petry said. "We were skating, we were moving the puck well, we were playing a simple game and I think towards the end of the first we were trying to force things, got a little sloppy. The second period was really sloppy, (Price) bailed us out several times.
"Was it a bad bounce? Sure. Should I have been sitting in the crease? You know, probably not. But I don't think the second period is the way the way we can play. We have to have consistent 60-minute games like we came out and ended to start that first period."
Vrana teamed up with linemates T.J. Oshie, who had two assists, and Evgeni Kuznetsov to make it 3-1 with his 23rd goal at 14:51. It was Vrana's ninth multipoint game this season.
Video: WSH@MTL: Vrana capitalizes on aggressive forecheck
"The line is clicking pretty good, we create chances all the time," said Vrana, who has 11 points (eight goals, three assists) during his streak. "This month I might be the one to have the most at the end of it, but you never know. Once we're going to create more chances, you know, they both can score as well. So it's not just about me."
Dale Weise, playing in his 500th NHL game, scored his first goal since Dec. 27, 2018 at 7:30 of the third to draw Montreal within 3-2.
Nicklas Backstrom made it 4-2 when he scored into an empty net with 23 seconds remaining.
Montreal is 4-2-0 since an 0-7-1 during an eight-game winless streak.
"You can take some positives out of our third period but it's not a complete effort from us," Weise said. "I don't know how happy we can be about that. You know, [Price] had to bail us out quite a bit tonight. We got off to a good start, and then kind of lulled, and then we put a push on in the third, which is just since I've been here, it's kind of been the norm for our team."
They said it
"It wasn't an easy game for him at all. There were some good chances against, and a lot of traffic, and they made pretty big push in the third. And I thought, as expected, a first game after a break is scrambly and there were mistakes by both teams, and so a difficult one for a goaltender to play. So I thought he had a strong game." -- Capitals coach Todd Reirden on Braden Holtby
"Every loss hurts but at this point these are all big games this whole week. And moving forward from there we have to get on a run here if we want to be in the playoffs, and I think every guy in here wants to accomplish that. But we have to have the right effort the majority of the time and we can't have those lapses like we did in the second (period) there." -- Canadiens defenseman Jeff Petry
Need to know
The Capitals' record is their second-best through 50 games, behind the 2015-16 season, when they went 37-9-4 with 78 points. … Holtby is 14-2-2 with a 1.69 goals-against-average and a .943 save percentage in 19 games against the Canadiens. … Vrana has scored 22 of his 23 goals at even strength, the third-most in the NHL behind Auston Matthews of the Toronto Maple Leafs (25) and Ovechkin (23). … Washington is 13-2-0 against the Atlantic Division. … Canadiens defenseman Marco Scandella's assist on Petry's goal was his first point in 10 games since he was acquired in a trade with the Buffalo Sabres on Jan. 2.
Capitals: Host the Nashville Predators on Wednesday (7:30 p.m. ET; NBCSN)
Canadiens: At the Buffalo Sabres on Thursday (7 p.m. ET; MSG-B, TSN2, RDS, NHL.TV)
Video: Holtby, Capitals double up Canadiens, 4-2