Cut each squash in half; discard seeds. Place cut side down in a 3 quart rectangular baking pan. Bake in preheated 350 F oven 50-55 minutes or until tender. Sauté beef, onion and celery in a large frypan until meat is browned; drain off any fat. Blend in flour, salt and sage. Stir in milk. Cook over medium heat, stirring constantly, until mixture just comes to a boil and thickens. Stir in cooked rice. Turn squash cut side up in pan; fill squash cavities with equal amounts of meat mixture. Return to oven and bake an additional 30 minutes. Top with cheese; bake 3 minutes longer.
Yield: 3 servings.