In a large skillet, cook beef over medium heat until no longer pink. Stir in the tomato sauce, beans, corn, green chilies, onion, chili powder, cumin, garlic powder and oregano; heat through., In an 11x7-in. baking dish coated with cooking spray, layer half of the tortillas, beef mixture and cheese. Repeat layers. Bake, uncovered, at 350° for 25-30 minutes or until bubbly. Freeze option: Cool unbaked casserole; cover and freeze. To use, partially thaw in refrigerator overnight. Remove from refrigerator 30 minutes before baking. Preheat oven to 350°. Bake casserole as directed, increasing time as necessary to heat through and for a thermometer inserted in center to read 165°.