Lay out a 12 inch square or a bit larger of foil.

Dice the sweet potato, mushroom, and onion into the center of the foil.

Add the butter or oil.

Sprinkle with onion powder, salt, and pepper.

Wrap the foil around the diced vegetables, rolling the edges of the foil under so it will hold together.

Wrap in the opposite direction with a second piece of foil.

Grill over medium heat for about 20 minutes.

Unwrap a corner, and check to make sure the sweet potatoes are tender. Be careful when you open the foil, because steam can build up.

Remove from heat and let the foil packs cool for about 5 minutes before serving.

Enjoy!