Vannelli beat Brandon goaltender Jordan Papirny just 32 seconds into OT on the power play.
Miles Koules, Markus Eisenschmid and Trevor Cox also scored and Marek Langhamer stopped 26 shots for the Tigers (16-5-3), who maintained their two-point lead atop the Eastern Conference.
Jesse Gabrielle scored twice for the Wheat Kings (13-11-1), while Eric Roy added a single and Papirny finished with 26 saves.
RAIDERS 1 BRONCOS 0
PRINCE ALBERT, Sask. — Carson Perreaux scored the lone goal of the game to lift the Raiders past Swift Current.
Perreaux's goal 10 minutes into the first period was all Prince Albert (14-8-2) needed in a game featuring just one penalty to the Broncos in the second.
The loss, and Medicine Hat's win, kept the Broncos (15-10-3) from tying the Tigers atop the Eastern Conference.
Cole Cheveldave finished with 26 saves for the Raiders, while Landon Bow stopped 30 shots for Swift Current.
SILVERTIPS 3 HURRICANES 2
LETHBRIDGE, Alta. — Tyler Sandhu gave the Silvertips the only lead they would need against the WHL's worst team.
Sandhu scored 5:45 into the third after Ivan Nikolishin tied the game for Everett just 56 seconds into the period.
Jujhar Khaira also scored and Austin Lotz had 16 saves for league-leading Everett (17-4-4).
Josh Derko and Jamal Watson scored for lowly Lethbridge (3-18-4), while Corbin Boes stopped 29 shots.
ICE 4 REBELS 3
RED DEER, Alta. — Tim Bozon scored in the third period as Kootenay edged the Rebels.
Jagger Dirk, Luke Philp and Zak Zborosky also scored for the Ice (13-11-2), who overcame a 2-0 deficit in the first period.
Dominik Volek scored twice for Red Deer (11-12-1), and Evan Polei added a single.
Jayden Sittler stopped 27 shots for Kootenay after replacing starting goaltender Wyatt Hoflin, who allowed three goals on 12 shots. Patrik Bartosak stopped 39 shots for the Rebels.
ROYALS 4 ROCKETS 1
KELOWNA, B.C. — The Royals handed the Rockets their first loss in 10 games.
Ben Walker, Tyler Soy, Austin Carroll and Brandon Fushimi scored for Victoria (15-10-1), which came alive in the third period with three goals.
Tyson Baillie had the lone goal for Kelowna (16-3-2).
Patrik Polivka finished with 26 saves for Victoria, while Jordon Cooke allowed all four goals on 19 shots in Kelowna's net.
CHIEFS 5 GIANTS 4
SPOKANE, Wash. — Carter Proft scored just over a minute into overtime as the Chiefs rallied past the Giants.
Jeremy McIntosh, Mike Aviani, Mitch Holmberg and Connor Chartier also scored for Spokane (16-7-1), which scored twice in the third period to come back from a 4-2 deficit.
Cain Franson, Trent Lofthouse, Carter Popoff and Dalton Thrower scored for Vancouver (10-11-5).
Chiefs goalie Eric Williams made 28 saves, while Payton Lee finished with 32 stops for the Giants.