Markus Granlund scored the only goal of the shootout in the top of fourth round, and then Markstrom made the save on William Karlsson to end it.
"I think everyone's jelling together," Horvat said. "Everyone's ambitious to prove ourselves, that we can be a good contender, and so far, we're proving that."
Max Pacioretty and Ryan Reaves scored for the Golden Knights (4-4-1), who lost for the first time in four games. Marc-Andre Fleury made 24 saves.
"They were quick. They were fast, quick on the forecheck," Fleury said. "They put a lot of pressure on our guys. I liked the way we battled back though."
Pacioretty scored for the first time in seven games at 1:18 of the second period to give Vegas a 1-0 lead.
But Horvat scored twice in 1:04 to give the Canucks the lead. He deflected a Loui Eriksson shot at 4:22 to tie it 1-1, and then scored on a breakaway at 5:26 to make it 2-1.
"He's a confident player, and he should be," Green said. "He's a good player in the League, and I think Bo's game has really picked up over the last stretch here. He'd be the first to admit that his game was a little loose early. He's tightened things up defensively, and when you do that, usually good things happen."
Horvat has four goals and one assist in a four-game point streak.
"I thought our first period and second period, I thought we played well," he said. "I thought we got on the forecheck pretty well and held them to limited chances in the third. We knew they were going to come hard. It's tough to maintain zone time, but I thought we did a good job shutting that team down."
Reaves scored his second goal in as many games at 17:39 to tie it 2-2. He took a drop pass from William Carrier and beat Markstrom blocker side.
