Prepare stuffing mix according to package directions. Spray a 13x9-inch disposable foil pan with cooking spray. Whisk together soup and milk.
Place cooked chicken in pan and layer with ham, Swiss cheese, 1 cup cheddar cheese, soup mixture and stuffing. Sprinkle with remaining cheddar cheese.
Cover with plastic wrap and aluminum foil. Label and freeze.
When ready to cook, thaw in refrigerator overnight. Set out on the counter for 30 minutes while preheating oven to 350°F.
Remove plastic wrap and foil, returning the foil loosely. Bake, about 45 minutes. Remove foil and bake an additional 10 minute