Cook ground chuck and diced onion in a Dutch oven, stirring until meat crumbles and is no longer pink. Drain meat mixture, and return to Dutch oven.
Stir in chicken soup, diced tomato and green chiles, and beans.
Layer half of the tortillas evenly into 2 lightly greased 13- x 9-inch baking dishes. Top each with one-fourth of meat mixture and one-fourth of cheese cubes. Repeat layers with remaining tortillas, meat mixture, and cheese.
Bake at 350° for 30 minutes or until cheese is melted.
* Pinto beans may be substituted for ranch beans.
Note: Freeze casserole up to 1 month, if desired. Thaw in refrigerator overnight, and bake as directed.