- To freeze and bake later, prepare mixture as directed above except do not sprinkle with cornflakes. Place into casserole or large freezer container. Cover tightly; freeze up to 3 months. To thaw, place in refrigerator 24 hours or until thawed. Heat oven to 350°F. Pour macaroni mixture into ungreased 2-quart casserole dish, if necessary. Bake, covered, 30 minutes. Uncover; sprinkle with cornflakes. Continue baking 10-15 minutes or until heated through.