Heat oven to 325°F Spray a 2 quart casserole dish with non stick spray.
Peel potatoes and cut into thin slices.
In a bowl combine mushroom soup and milk.
Place a layer of potatoes in the bottom of the casserole dish. Drizzle a scoop of the mushroom/milk mixture over the potatoes followed by a sprinkling of the cheese, the seasoned salt and a sprinkle of the dried onions. Repeat each layer the same way (you will probably have about 3 layers) ending with a sprinkle of cheese.
Bake in 325F oven approximately 1 1/2 hours or until top is browned and bubbly.