In a large bowl, combine the ground beef, onion, milk, bread crumbs, egg, worcestershire sauce, and taco seasoning.Use your hands to work the mixture until everything is completely, and evenly combined.
Roll the meat mixture into 1.5 inch meatballs. It should make 24-26 meatballs.
Pour 1/4 cup of the enchilada sauce into the bottom of a large casserole dish. Arrange the meatballs in the dish, then pour the remaining enchilada sauce over the meatballs. Sprinkle cheese over the top.
Bake for 40-50 minutes or until the edges are bubbly and the meatballs are cooked through to 165˚F internal temperature.