Preheat your oven to 375°F (190°C) and lightly grease a 9x13-inch baking dish.

In a large skillet over medium heat, cook the ground beef or turkey with the onion and garlic until the meat is browned and the onion is tender. Drain off any extra grease.

In a large bowl, combine the cooked meat mixture with potatoes, carrots, and green beans. Add the cream of mushroom soup, milk, Italian seasoning, salt, and pepper. Stir until everything is evenly coated in the creamy sauce.

Spread the mixture evenly in your prepared baking dish. Cover the top tightly with foil to trap the steam while baking.

Bake for 45 minutes. Remove the foil, sprinkle the cheddar cheese over the top, and return the dish to the oven.

Continue baking uncovered for another 15 minutes, or until the cheese is bubbly and melted and the vegetables are fork-tender.

Let the casserole sit for about 5 minutes before serving — it will thicken slightly and be easier to serve.