Heat oven to 350F. Spray 13x9-inch (3-quart) glass baking dish with cooking spray. In large bowl, mix soup, chiles, sour cream and milk until blended. Stir in chicken, tortillas and bell pepper. Stir in tomato and 1 cup of the cheese. Spoon and spread mixture in baking dish.
Cover with foil. Bake 40 minutes. Uncover; sprinkle with remaining 1/2 cup cheese. Bake uncovered 5 to 10 minutes longer or until cheese is melted and mixture is bubbly. Let stand 5 minutes.