Preheat oven to 350°F To make cornbread, combine first 5 ingredients and pour into a greased shallow baking dish. Bake for 20-25 minutes. Remove from oven and cool.
To make dressing, crumble dried white bread slices, cornbread, and crackers. Mix together and set aside.
Sauté chopped celery and onion in butter until transparent, approximately 5-10 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.