butter
Potatoes
Onions, sliced thin
Salt & pepper
Aluminum foil

Scrape foil with butter. Peel potatoes, cut thin slices. Put potatoes in center of foil (approximately 2 potatoes medium to 1 piece of foil). Top with onion. Add salt and pepper. Put 1 pat of butter on top. Seal foil by folding ends together. Then ends. Grill at medium temperature about 20 minutes, turning 1-2 times until potatoes are soft when stuck with a fork.