Cheesy Broccoli and Rice Casserole

Ingredients
2 (10 ounce) boxes frozen chopped broccoli, thawed
2 cups cooked rice
8 ounces shredded cheddar cheese
2 (10 3/4 ounce) cans cream of chicken soup (or you use 1 can each cream of chicken and cream of mushroom)
1 small onion, chopped
2 tablespoons butter

Directions
Cook onion in butter in large skillet until soft.
Add remaining ingredients and cook just until cheese is melted.
Put in 2 quart casserole dish.
Bake at 350 (uncovered) for 1 hour.
To make ahead and freeze: Mix all ingredients together (start with your rice cooked, not raw) and spoon into two or even three smaller casserole dishes, cover, label and freeze. If you thaw overnight, just cook the one hour. If cooking from frozen state, add ten minutes or so, check for doneness. Many thanks to Tornado Ali, for her wonderful tips for freezing this.

Source: allrecipes.com