Busy Day Casserole

4 med. potatoes, peeled and sliced
4 med. carrots, peeled and sliced
1 Tbsp. minced onion
1 lb. ground beef, cooked and crumbled
1 can cr. of mushroom soup
Salt and pepper to taste
Combine ingr. with 1 1/2 cans water. Bake 1 1/2 hrs. 350 degr.