Halve squash crosswise; remove seeds. Place cut sides down in 2-quart rectangular baking dish. Add 1/4 cup water. Cover with vented plastic wrap. Microcook on high power 13 to 15 minutes or until squash is tender when pierced with fork; rearrange once for even baking. In a large skillet cook sausage, mushrooms, sweet pepper, onion, and garlic over medium heat until sausage is no longer pink; stir to break up sausage. Drain off fat.
Preheat oven to 350 degrees F. Scrape pulp from squash (about 3 cups). Wipe out baking dish; coat with nonstick cooking spray. Spread half the squash in dish. Add half the sausage mixture and half the olives. Sprinkle with seasoning and 1/8 teaspoon black pepper. Top with half the sauce and half the cheese. Top with remaining squash, sausage, olives, and sauce. Bake for 30 minutes. Sprinkle with remaining cheese. Bake for 5 minutes or until cheese is melted. Let stand 10 minutes. Sprinkle with parsley. Makes 6 servings.