In a large mixing bowl, combine the cooked rice, diced ham, shredded cheddar cheese, cream of mushroom soup, milk, frozen peas, salt, and black pepper. Mix well.
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 the casserole cool for a few minutes before serving.
Notes:
This casserole is perfect for using up leftover ham and can be customized with your favorite vegetables.