Brendan Gallagher and Rafael Harvey-Pinard scored for Montreal (30-39-6) which was eliminated from contention for the Stanley Cup Playoffs. Cayden Primeau, in his first start since Feb. 10, 2022, made 24 saves.
The Canadiens won 4-3 in a shootout at the Buffalo Sabres on Monday.
"We just didn't have the jump that we needed to create a little bit more," Gallagher said. "Give them credit, they were sound in their structure, making it really tough on us, and they made a play at the end."
Frost gave the Flyers a 1-0 lead at 3:41 of the second period. As a power play was expiring, Kevin Hayes circled behind the Canadiens goal and passed through the slot to Frost, who settled the pass and scored short side, past Primeau's blocker.
His second goal put Philadelphia ahead 2-1 at 17:45 of the third period when he finished a 2-on-1 rush with Joel Farabee. Frost skated up the wing, cut from the right face-off circle to the slot and beat Primeau high to the glove side.
"I was thinking pass like I usually do most of the way, and then I saw the second guy was going to over-backcheck," Frost said. "So, I switched it up last minute and ended up shooting."