Microwave the frozen broccoli for about 1-2 minutes to thaw.
In a large casserole dish, combine the cooked rice, diced chicken, cream of chicken soup, milk, eggs, and thawed broccoli. Stir everything well until mixed.
Top the mixture with shredded cheddar cheese, if desired.
Cover the casserole dish with foil and bake in the preheated oven for 15 minutes.
Remove the foil and bake for an additional 5-15 minutes until hot throughout and the top is slightly golden.
Serve the casserole warm.
Notes
Prepare ahead and store in the refrigerator for easy baking the next day.
Use fresh broccoli for better flavor and adjust seasonings as per taste.