Cut each squash in half lengthwise; remove seeds. Place squash, cut sides down, in a 3-quart rectangular baking dish. Bake, uncovered, in a 350 degree F oven for 45 minutes.
Meanwhile, in a large skillet cook turkey sausage, onion, and garlic until sausage is brown and vegetables are tender. Remove from heat and drain well. Stir in pears, ricotta cheese, and parsley.
Turn squash cut sides up in the baking dish. Season with salt and pepper. Spoon sausage mixture into the baked squash, mounding as necessary. Bake, covered, about 20 minutes more or until squash is tender.
Stir together bread crumbs and melted margarine or butter; sprinkle over filling in squash. Bake, uncovered, 3 to 5 minutes more or until crumbs are toasted. Makes 4 servings.