Broccoli and Corn Bake

2  (10 oz.) pkgs, frozen chopped broccoli, thawed and drained
(can use an equivalent amount of fresh broccoli, steamed and
chopped)
1 small onion, diced
1/2 cup celery, diced

1 cup of corn niblets (frozen or canned)
1  1/2 cups long grain rice, under cooked
1 cup milk
1  (10.5 oz.) can cream of mushroom soup (homemade is best)
8 oz. Velveeta cheese or Cheese Wiz
1/2 cup butter ( 1 stick)
1/2 tsp. black pepper
Topping
1 tube Ritz crackers, crushed
4 Tbs. butter, melted (1/2 stick)

Combine the broccoli, onion, celery, corn, and rice in a mixing
bowl.  In another bowl combine the 1/2 cup butter, mushroom
soup, milk and cubed Velveeta cheese.  Microwave until the
cheese has melted, about 2-3 minutes and stir until smooth.   
Pour over the broccoli mixture and mix until combined.   Pour
into a 2 quart casserole dish that has been sprayed with nonstick
spray.  
Combine the crushed Ritz crackers and butter and sprinkle
evenly over the top.    Place in a 325 degree oven for 50 -55
minutes.  It will be just starting to brown.