Heat oven to 350 degrees. Spray 11x7-inch glass or ceramic baking dish with cooking spray.
Cook sausage in large skillet over medium-high heat 3-4 minutes or until beginning to brown, stirring frequently. Add squash, celery and onion; cook 5 minutes or until sausage is no longer pink and vegetables are tender, stirring frequently. Add garlic, salt and pepper; cook and stir 1 minute. Remove from heat; gently stir in cornbread
Pour spagetti sauce over bottom of baking dish. Spoon stuffing mixture into bell pepper halves, mounding as necessary. Arrange in baking dish; cover with foil.
Bake 40-45 minutes or until peppers are almost tender. Sprinkle with cheese; bake, uncovered, an additional 10 minutes or until peppers are tender.
TIP: For best flavor, use cornbread without a lot of added sugar.