Scalloped Potatoes

Preheat oven 400F. Lightly spray a 2 quart casserole with vegetable spray.
Arrange a layer of potatoes in casserole, then sprinkle with some of onion, flour, salt and pepper.
Continue to layer until all potatoes, onion, flour salt and pepper are used.
Dot top with margarine, then pour milk over all.
Bake 20 min, then reduce heat to 350F and bake 50 to 60 min longer or until tender.