When my Maternal Grandmother married for the second time and moved to his home in New Mexico and began feeding 12 hungry step-children, she began sending Mom some great recipes from the southwest (not that Oklahoma wasn't southwest as well!). This is one of the recipes she sent.
Brown ground beef and onions together. Drain off excess grease. Add cream of mushroom soup, milk and green chilies diced. allow to slowly heat through as you prepare the pan.
Use a spray oil to coat a 9" x 13" pan. Lay tortillas in bottom of pan so they overlap. and come up the sides slightly. Spread with half of the meat mixture. top with half of the cheese. Repeat with remaining tortillas, meat mixture and cheese.
Bake for 35-40 minutes or until cheese is melted and bubbly.
Alterations: Instead of the cream of mushroom soup and milk, try adding a large can of pinto beans with their juice and taco seasoning. Later with tortillas and cheese as before.
Alteration 2: Use cream of chicken soup instead of cream of mushroom, and shredded chicken instead of beef.