Luke Bertolucci had the other goal for Edmonton (36-11-5), which earned its sixth straight win.
Joey Leach and Sam Reinhart replied for Kootenay (23-26-2), which came in having earned 13 of a possible 14 points in its last seven games.
Bertolucci opened the scoring at 7:44 of the first, firing a shot past Kootenay netminder Wyatt Hoflin.
Foster, Corbett and Lazar scored 1:25 apart early in the second to put Edmonton ahead 4-0.
Foster finished a nice passing play with Michael St. Croix at 2:06 before Corbett scored on a wrist shot just seven seconds later. Lazar made it 4-0 at 3:31 as Henrik Samuelsson drew an assist to extend his points streak to six games (four goals, eight assists).
Leach scored Kootenay's first goal of the game at 14:18, beating Oil King goalie Laurent Brossoit. Reinhart made it 4-2 on a two-man power play with 2:54 remaining in regulation, extending his points streak to 14 games (13 goals, 10 assists).
That tied Reinhart with Portland's Ty Rattie for the longest active streak in the WHL. Rattie has accumulated 26 points during his run.
Hoflin finished with 39 saves for the Ice while Brossoit stopped 31 shots.