Kelowna leads the best-of-seven series 3-0.
Leon Draisaitl, Gage Quinney and Dillon Dube also scored for the Rockets, while Jackson Whistle made 26 saves for the win.
Morgan Klimchuk, Nolan Patrick and Tim McGauley replied for Brandon. Jordan Papirny stopped 27 shots in net for the Wheat Kings.
Kelowna won despite going 0 for 5 on the power play. Brandon was 1 for 3 with the man advantage.