Pre-heat the oven to 350 degrees. Add potatoes to a large pot. Add enough water to cover the potatoes and bring to a boil over high heat. Cook for 10-12 minutes or until the potatoes are almost tender. Drain.
Lightly grease a 13×9 inch casserole dish. In a bowl mix together the cream of mushroom soup, milk, ranch dressing, 1 cup of the cheese, salt and pepper. Pour over potatoes in the casserole dish.
Sprinkle remaining cup of shredded cheddar cheese and the crumbled bacon over the top. Place into the oven and bake uncovered for 25-30 minutes or until the potatoes are tender.