COOK the beef in a 10-inch skillet over medium-high heat until it's well browned, stirring often. Pour off any fat.
STIR the soup, salsa, milk, tortillas and half the cheese in the skillet. Spoon the beef mixture into a 2-quart shallow baking dish. Cover the baking dish.
BAKE at 400°F. for 30 minutes or until the beef mixture is hot and bubbly. Sprinkle with the remaining cheese.