1. Preheat oven to 375°. Brown sausage in a large sauté pan over medium heat, stirring until it crumbles and is no longer pink. (Do not drain.) Add onion, celery, and garlic; sauté 5 minutes. Add apple, and sauté 3 minutes or until apple begins to soften; transfer to a large bowl, and let cool 10 minutes.
2. Add remaining ingredients to sausage mixture, stirring until well blended. Spoon into a well-greased 13- x 9-inch baking pan. Bake at 375° for 40 minutes or until top is crusty and brown.