In a large bowl, toss the potatoes with olive oil, garlic powder, 1/2 teaspoon salt and black pepper to taste. Toss evenly to coat.
Transfer to a large sheet, 18 x 18 inches, of Reynolds Wrap® Heavy Duty Foil on a flat surface.
Place the ingredients in the center of the Reynolds Wrap® Heavy Duty Foil. Form a packet by bringing two ends of the foil together and fold twice to seal, leaving room for steam.
TO GRILL: Grill covered over medium heat for 30 minutes, shaking the bag every 10 minutes so the bottom of the potatoes don’t burn. Open carefully and top with 1/8 teaspoon salt, lemon zest and parsley.
IN THE OVEN: Bake in a preheated 400° F oven for 35 to 40 minutes, shaking the bag halfway through. Open carefully and top with 1/8 teaspoon salt, lemon zest and parsley.