In a large bowl, combine the cooked rice, shredded chicken, cream of mushroom soup, milk, shredded cheddar cheese, and frozen peas and carrots. Mix well.
Season with salt and pepper to taste.
Transfer the mixture to a greased baking dish and spread it out evenly.
Bake in the preheated oven for 45 minutes, or until the casserole is bubbly and the top is golden brown.
Let it cool for a few minutes before serving.
Notes:
You can substitute the cream of mushroom soup with cream of chicken soup if preferred.