Add potatoes to a large mixing bowl. Drizzle with oil and stir to coat. Add salt, pepper, and ranch mix. Stir until the potatoes are well coated.
Transfer potatoes to a square sheet of heavy-duty aluminum foil. (Don't use the regular kind, it'll break!) Group together in the center of the foil. Fold one side over the potatoes and then the other side so they are overlapping. This will create a long rectangle. Fold up the ends to seal everything in.
Place potato packet on the hot grill, seam side up. Grill for 10 minutes. Flip and grill for another 10 minutes. Remove from heat.
Place potato packet on a serving plater and cut an uppercase I in the middle of the foil. Carefully open the sides of the foil pack and fold them down. Sprinkle the potatoes with cheese, bacon, and parsley. Serve immediately.
If using mini red potatoes, cut in half lengthwise. If using regular red potatoes, cut into quarters (bite-sized pieces).
I cooked my bacon in the oven while the potatoes grill. You could cook your bacon on the grill if you prefer. Once the cheese is added to the potatoes, place the plate in the warm oven to help the cheese melt.
You can serve these potatoes right out of the foil or transfer them to a serving bowl before adding toppings.