O'Reilly scored twice in the first period, netting the game's first goal after a pass from Vladimir Tarasenko at the 11:57 mark. The center then struck again on a late power play, firing a Tarasenko pass from behind the net into the Hurricanes' goal with just five seconds remaining in the period.
An empty-net goal at 16:50 of the third period capped off the night for O'Reilly, giving him his first hat trick after 664 career NHL games. Robby Fabbri also scored for the Blues, his first goal since Dec. 28, 2016.
Jaccob Slavin accounted for Carolina's only goal, a power-play effort on a slapshot from beyond the circle at 19:34 of the first period. The goal was Slavin's first of the year and ended a 24-game drought dating to last season.
Nikita Kucherov and Steven Stamkos had three points apiece, and Tampa Bay held Connor McDavid off the scoresheet for just the second time this season in a win over visiting Edmonton.
Kucherov had two goals and an assist while Stamkos scored and had two helpers. Brayden Point and Yanni Gourde posted a goal and an assist for the Lightning, who beat Edmonton for the ninth time in 10 games in Tampa Bay.
Goalie Andrei Vasilevskiy stopped 33 shots in his 11th start for the Lightning and improved to 8-2-1 this season.
Connor Brown, Mitch Marner and Nazem Kadri each scored one goal, and Toronto defeated visiting Vegas.
Goaltender Frederik Anderson made 36 saves for the Maple Leafs, who had lost two in a row and four of their past five games at home.
The Knights lost center Erik Haula after he took a check from Patrick Marleau of Toronto about five minutes into the third period. Haula was removed from the ice on a stretcher with an apparent leg injury.
Defenseman Neal Pionk scored the tiebreaking goal on a terrific end-to-end rush with 2:44 remaining in the third period, and New York overcame a two-goal deficit to beat visiting Montreal.
Kevin Hayes set a career high with three assists by setting up Chris Kreider's first-period tally before earning helpers on goals by Tony DeAngelo and Pavel Buchnevich. Mika Zibanejad finished the scoring with New York's second short-handed goal of the game at 18:12 of the third period.
Henrik Lundqvist made 31 saves and picked up his 436th career victory.
Mark Stone and Colin White tallied twice apiece for Ottawa, which scored six unanswered goals to beat visiting New Jersey.
Their second win in the last eight games came at an opportune time for the Senators, who were embroiled in controversy Monday when a video was leaked of several players mocking the coaching staff in Arizona last week.
Thomas Chabot and Ryan Dzingel opened and closed the six-goal outburst for the Senators, respectively, while Magnus Paajarvi added an empty-netter in the third period. Goalie Craig Anderson earned the win by recording 30 saves before he exited late in the third due to an injury.