To make the cornbread, combine all ingredients and pour into a greased shallow baking dish. Bake for approximately 20 to 25 minutes. Remove from oven and let cool. To make the dressing, crumble dried white bread slices, cornbread and crackers.
Mix together and set aside. Sauté chopped celery and onion in butter until transparent, approximately 5 to 10 minutes. Pour over corn bread mixture.
Add stock, mix well and add salt, pepper, sage, and poultry seasoning. Add beaten eggs and mix well. Add oysters and mix. Pour into a greased pan. Bake for about 45 minutes.