Cook ground beef with onion in skillet and drain. Add both cans of tomato soup, garlic, oregano, salt and pepper. Cook over low heat about 15 minutes to blend flavors.
Cook elbow macaroni, drain and rinse with cold water to cool a little (doesn't have to be cold, you just don't want the cheeses melting yet). Add milk, egg and cheeses and mix.
Using a large, deep casserole, add in layers: 1/2 the macaroni mixture, 1/2 the beef mixture, then repeat. Top with a little extra cheese, if desired. Bake 350 for about 30 minutes or until bubbling around the edges.