Preheat the oven to 350 degrees.
Saute onion in the margarine.
Add broccoli and cook until completely thawed.
In a saucepan, heat the soup, milk, and cheese until it melts together into a thick sauce.
In a casserole dish, add the soup mixture, the cheese mixture, and the rice.
Next, add the chicken and stir well.
Sprinkle the casserole mixture with bread crumbs.
Bake for 35 to 45 minutes at 350 degrees.