1 Place in center of tin-foil. 2  Slice onions and red pepper and pile on top of potatoes. 3  Sprinkle the minced garlic, soup mix, thyme, and salt and pepper over the piled veggies. 4  Dot with cubes of butter. 5  Wrap tightly in the tin-foil, and cook on the grill about 30-45 minutes, or until potatoes are tender. Slice onions and red pepper and pile on top of potatoes. 2  Sprinkle the minced garlic, soup mix, thyme, and salt and pepper over the piled veggies. 3  Dot with cubes of butter. 4  Wrap tightly in the tin-foil, and cook on the grill about 30-45 minutes, or until potatoes are tender.