Spray a large piece of heavy-duty foil with nonstick cooking spray.
Place the potatoes and onion on the foil.
Top with the butter, garlic, salt, and pepper.
Fold the foil around the potatoes and seal the edges tightly to form a packet.
Place the foil packet on the grill or campfire over medium heat.
Cook for 20–30 minutes, flipping the packet halfway through, until the potatoes are tender.
Carefully open the foil packet and serve warm.
Video
Notes
We used heavy duty foil to make sure that it doesn’t break when cooking. Refrigerate the leftovers in an airtight container for up to 5 days. Oven InstructionsPreheat the oven to 400°F. Place the prepared foil packets on a baking sheet and bake for 35–45 minutes, or until the potatoes are fork tender. Carefully open the packets, as hot steam will escape, top with cheese and place back in the oven for 5 minutes to melt the cheese. Then the campfire potatoes are ready to serve immediately.