In a large bowl, combine the Alfredo sauce, broccoli, chicken and cheeses. Spoon into pasta shells. Place in a greased 13x9-in. baking dish.
Cover and bake at 350° for 30-35 minutes or until heated through. Freeze option: Cover and freeze unbaked casserole. 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°.Yield: 7 servings.