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, carrots, celery and garlic; cook 10 minutes or until onion is translucent, stirring frequently. Transfer mixture to a large bowl; add remaining ingredients; stir well. Pour into a buttered 4-quart casserole. Bake covered for 60 minutes.