In a large skillet over medium heat, brown the ground beef. Drain any fat.
Stir in onion and celery and cook until tender, about 4-5 minutes.
Transfer beef mixture to a greased 9x13-inch casserole dish. Stir in condensed soups, rice, mushrooms (if using), and milk. Season with salt and pepper. Mix well.
Cover and bake for 45 minutes. Uncover, and top with cheese. Bake an additional 25 minutes, or until cheese is melted and rice is tender.
Let rest 10 minutes before serving.
Notes
Keep leftovers in an airtight container in the refrigerator for 4 days and in the freezer for 3 months.