French Dip Scalloped Potatoes

4 large baking potatoes; peeled, thinly sliced
1 (10.75 ounce) can cream of mushroom soup
1/2 cup melted butter
16 ounces French onion dip

Place sliced potatoes in crock pot. Pour in soup and melted butter; stir. Cover and cook on LOW for 6-8 hours until potatoes are tender. Stir in French onion dip 30 minutes before serving; heat through.