Preheat oven to 325° F. In a large saucepan or stockpot, cook sausage over medium-high heat, stirring frequently, until thoroughly cooked and no longer pink. Add mushrooms, onion, bell pepper, celery and garlic; cook 10 to 12 minutes or until onion is translucent, stirring frequently. Transfer mixture to a large bowl; add remaining ingredients and stir well. Pour into a buttered 3- or 4-quart casserole dish. Bake covered for 50 to 60 minutes.