The Blues are 13-2-4 since Hitchcock took over for the fired Davis Payne last month and are now tied with Vancouver for the fifth seed in the Western Conference.
St. Louis has recorded at least one point in six straight games (5-0-1) and the club has suffered just one regulation loss over its last 12 contests (9-1-2).
After dropping a shootout decision Saturday in Nashville, the Blues won a wild home game against Columbus on the following night. St. Louis trailed 3-2 heading into the third period, but the Blues charged back for a 6-4 victory.
T.J. Oshie added a goal and an assist for St. Louis, which scored a season- high in goals to back Jaroslav Halak's 28-save effort.
Tonight marks the first test of a two-game road trip. The Blues, who will also visit Phoenix on Friday, are 6-6-3 as the visiting team this year compared to a superb 13-3-1 record at home.
The Avalanche, meanwhile, will aim for a third straight victory tonight after winning the first two tests of a four-game homestand. Colorado has now won six straight on home ice to improve its record at the Pepsi Center this year to 10-9-0.
O'Reilly was the fifth skater to score in the shootout as he made a move and lifted the puck over Ilya Bryzgalov. Matt Read had the last shot of the game and beat Jean-Sebastien Giguere, but rang his wrister off the crossbar.
T.J. Galiardi and Gabriel Landeskog each had a goal for the Avalanche, who have won three of their last four games. Giguere stopped 31 shots in the win.
"It's a big two points for us and we sure worked hard for it tonight," said Landeskog. "They are a very good team and they came out flying. We didn't match their work ethic at first, but we came out in the end."
The Avalanche, who will close this residency Friday against Tampa Bay, last suffered a loss on home ice on Nov. 28 against Dallas.
Colorado forward David Jones (groin) and defenseman Kyle Quincey (groin) are questionable for tonight's game. Jones has sat out the last three games, while has missed the last two.
The Avs have won eight of nine and nine of their last 13 versus the Blues, taking five straight as the host in this series.