Brown the ground beef in a large skillet over medium-high heat. Drain off any excess grease.

Add the onion and garlic to the skillet and cook until softened, about 5 minutes.

Stir in the sliced mushrooms and cook until tender, about 5-7 minutes.

In a bowl, combine the cooked rice, cream of mushroom soup, and milk. Stir until well combined.

Pour the rice mixture over the beef and mushroom mixture in the skillet. Stir to combine.

Pour the mixture into a greased 9x13 inch baking dish.

Sprinkle the shredded cheddar cheese over the top.

Bake in a preheated oven at 375°F (190°C) for 20-25 minutes, or until bubbly and heated through.