A barbecue grill assembly is disclosed having a dual mode of operation for cooking with charcoal briquettes or with a burner element. The firebox of the grill includes a burner element near the floor thereof and an aperture in one of the sidewalls for receiving a tray member. The tray member has channels for receiving charcoal to be ignited by the gas burner and which, in its 180.degree. inverted position, acts as a shield for the burner. Positive locking is accomplished with spring-clips and by bimetallic lever arms which lock the tray in the tracks when heated.