Broccoli Rice Casserole

1 14 oz. pkg (4-1/2 c) uncooked packaged precooked rice
2 10 oz. pkgs. frozen chopped broccoli
1 cup chopped celery
1/2 cup chopped onion
4 tablespoons butter or margarine
2 can condensed cream of mushroom soup
1 cup milk
1 16 oz. jar processed american cheese spread

Cook rice according to package directions; set aside. Cook broccoli according to package directions; drain well. Cook celery and onion in butter or margarine till tender, but not brown. Combine soup, milk and cheese; stir in rice, broccoli, and celery mixture. Turn into two 2-quart casseroles. Bake at 350 for 40-45 minutes.