Heat oven to 350°F. Spray 11x7-inch (2-quart) glass baking dish with cooking spray. Spread 1/3 cup of the enchilada sauce in baking dish.
Heat contents of mesquite chicken pouch in microwave as directed on pouch. In medium bowl, mix chicken, 1/2 cup of the cheese and the sour cream. Spoon about 1/3 cup mixture evenly down center of each tortilla; roll up and place seam sides down over sauce in baking dish. Spoon remaining 1/3 cup enchilada sauce over tortillas. Cover with foil.
Bake about 25 minutes or until hot. Uncover; sprinkle with remaining 1/2 cup cheese. Bake uncovered 2 to 3 minutes longer or until cheese is melted. Sprinkle with lettuce and tomato.