In large bowl, combine shredded chicken, onion, taco seasoning, green chiles, large enchilada sauce, and 1 cup Mexican cheese.
Pour a thin layer of enchilada sauce on the bottom of a 9″x13″ casserole dish.
Divide the chicken filling among the tortilla shells, roll loosely, and place them side by side in the casserole dish seam side down.
Top tortillas with the small can of enchilada sauce and remaining cheese.
Cover with plastic wrap and aluminum foil.
Cook in Oven from Frozen: Remove plastic before baking. Bake at 350F for 30 minutes covered then 10 minutes uncovered.
