Wash potatoes & slice them. Line flat cookie sheet with foil. Use enough foil so that you can enclose the potatoes. Separate bacon & line the cookie sheet with the bacon. Layer the sliced potatoes on top of the bacon. Chop onion in big pieces & spread on top of potatoes. Cut up margarine & place on top of potatoes. Sprinkle season-all on top of potatoes, onions & margarine.
Seal potatoes with another piece of foil. Cook at 375°F for 1 hour or until done. When done, open up top piece of foil & spread mozzarella cheese & cover until cheese is melted.
For the grill: prepare potatoes just like you would be cooking them in the oven. Place potatoes on the grill in the foil only. Cook for 1-1 1/2 hours.