Cut baked potatoes into 1-in. cubes. Place in a greased 13×9 inch baking dish. Sprinkle with salt and pepper.
In a small bowl, whisk together the sour cream and milk and pour over potatoes. Melt the butter than pour over then top of the potato mixture. Top with grated cheese. Cover with foil and bake for 25 minutes. Remove from oven and take off foil and sprinkle with crumbled bacon. Put back in the oven for 5 to 10 minutes.