First period sealed deal
St. Louis got two goals from Alexander Steen and another by Chris Stewart in the first period and that was the ballgame.
Brendan Gallagher's 10th of the season was the only score of the middle period.
Jaden Schwartz and Maxim Lapierre made it 5-1 in the third.
St. Louis outshot the Canadiens 29-26.
Icing on the cake
Jaden Schwartz and Maxim Lapierre scored third-period goals to complete the rout.
Brendan Gallagher snapped out of an 11-game scoring drought, batting his own rebound out of the air and past Jaroslav Halak.
It was the Canadiens' first even-strength goal in regulation since Dec. 7 in Buffalo: 356 minutes, 35 seconds.
Shots were 11-6 St. Louis.
It began with Alexander Steen's shorthanded goal, completing a 2-on-1 with T.J. Oshie four minutes in.
Three minutes later, Steen popped another one: his 24th, matching a career high.
Wide-open in the slot, Chris Stewart made it 3-0.
Alexei Emelin was on for all three St. Louis goals.
Shots were 12-8 for the home team.
Christmas road trip begins
Your Montreal Canadiens won't be back on Bell Centre ice until next year.
Between now and Jan. 4, the team plays in St. Louis, Nashville, Tampa Bay, Florida, Carolina and Dallas.
The Canadiens face two challenging games before a six-day Christmas break next week: the Blues Thursday night, the Predators on Saturday.
St. Louis sits second behind Chicago in the NHL's Central Division. The Blues have a plus-34 goal differential and are 13-3-2 at the Scottrade Center.
A week ago, the game shaped up as a clash between two of the league's best defence pairings: Andrei Markov and P.K. Subban vs. Alex Pietrangelo and Jay Bouwmeester. But Michel Therrien shuffled his Dmen against Phoenix, pairing P.K. with Josh Gorges and Markov with countryman Alexei Emelin.
Daniel Brière will be a healthy scratch against St. Louis.
In the interim, check out the Canadiens' Christmas card.