Barbashev pushed it to 3-0 at 9:09. He finished off a give-and-go return pass from Eichel on a 2-on-1 after Montreal forward Juraj Slafkovsky turned over the puck inside the Vegas blue line.
“If I put the puck down the wall, they don’t have a 2-on-0 on the other side,” Slafkovsky said.
Tanner Pearson made it 4-0 at 10:35 on a shot from the inside edge of the right face-off circle on a backhand pass from Noah Hanifin.
Kolesar scored at 17:02 for a 5-0 lead. He scored stick side on Montembeault, who dropped Zach Whitecloud’s shot from the point at his feet.
“When you’re minus-4, I don’t even know what to say,” Slafkovsky said. “You can’t really get worse, in my opinion, than tonight’s second period. So you can only play better and make better decisions with the puck because that was just stupid.”
Emil Heineman cut it to 5-1 with a power-play goal at 2:03 of the third period. Jayden Struble scored at 13:03 to make it 5-2.
Eichel one-timed Barbashev’s cross-ice pass on a 2-on-1 at 18:12 for the 6-2 final.
“They had a good night,” Cassidy said. “Let’s face it, in the third period we got off our game, they pushed us. I know it’s late, but at the end of the day, good on them to make a play.”
NOTES: Eichel has 32 points (seven goals, 25 assists) in 21 games. He is the fastest player in Golden Knights history to reach 30 points in a season. Mark Stone got his 30th point in his 24th game in 2020-21. … It was Eichel’s 15th three-point game with Vegas, tying William Karlsson for third in franchise history. Jonathan Marchessault had 25 three-point games with the Golden Knights, and Stone has had 20. … Vegas’ previous high for goals in a period this season was three, most recently in the third period of a 4-2 win at the Utah Hockey Club on Nov. 15. … The Golden Knights scored five goals in the first period of a 6-2 win at the Vancouver Canucks on March 9, 2019, and in the third period of a 7-2 win against the Anaheim Ducks on Feb. 5, 2023. ... Vegas defenseman Nicolas Hague played 15:09 and had one shot and four hits after missing eight games with an undisclosed injury.