In a large skillet, cook 1 pound of ground beef and onion over medium heat until no longer pink; drain. Stir in the soup, enchilada sauce, milk and chilies. Bring to a boil. Reduce heat; simmer, uncovered, for 20 minutes, stirring occasionally.
Meanwhile, in another skillet, cook remaining beef over medium heat until no longer pink; drain. Stir in the water and taco seasoning. Bring to a boil. Reduce heat; simmer for 5 minutes, stirring occasionally.
Place about 1/4 cup taco-seasoned beef down the center of each tortilla; top with 1/4 cup cheese. Roll up and place seam side down over meat sauce in skillet. Sprinkle with remaining cheese. Cover and cook for 1-2 minutes or until cheese is melted.