Ranchero Potatoes

4 sliced, cooked potatoes
1/2 Cup butter
2 tablespoons flour
1 Cup milk
1/2 Teaspoon salt
1/4 teaspoon pepper
1/2 Cup finely diced onion
1/4 Cup barbecue sauce
1 Cup grated cheese

- Layer 1/2 the potatoes in an 8x8 casserole dish. In a sauce pan melt the butter over medium heat; stir in the flour, add the milk gradually, stirring constantly, until thickened. Remove from heat add the salt, pepper, onions and BBQ sauce; stir in the cheese until melted. Pour 1/2 the sauce mix over potatoes; repeat the layers. Bake at 350°F for 25 minutes.