Preheat an outdoor grill for medium high heat and lightly oil grate.
Use either a 9x13 inch grill-safe baking dish OR a piece of foil large enough to hold all the ingredients. Layer with the potatoes, onions, pats of margarine, salt and ground black pepper. Sprinkle top with imitation bacon bits. Cover with foil and make sure you seal tightly so the margarine does not escape.
Grill over medium high heat for 45 to 60 minutes, or to desired doneness. Carefully open, arrange the cheese over all and allow a few minutes for the cheese to melt. Remove from grill and serve immediately.
