Grant scored three, including the winner, and helped on two more, and Joey Cupido, Dan Ball, Jackson Decker and Anthan Iannucci each added a goal apiece for Colorado (2-5). Chet Koneczny had three assists.
Dane Dobbie, Shawn Evans, Curtis Dickson, Dan MacRae, and Scott Ranger scored two goals each for Calgary (2-3), Jeff Shattler had a goal and five assists, and Daryl Veltman and Curtis Manning each scored.
Mammoth goalie Dillon Ward made 35 saves for the win.
Mike Poulin and Frankie Scigliano split time in Calgary's net, with Poulin giving up 12 goals on 29 shots, and Scigliano making three saves on five shots.