My method to coarsely chop oysters: drain & reserve liquor then pulse several times in blender.
About 1-1/2 hrs. before serving...In Dutch oven over med.-high heat melt butter and cook onions 5 mins. or until tender; remove from heat. Stir in oysters and liquor, bread cubes/crumbs, celery, s&p, thyme and poultry seasoning.
Spoon mixture into greased 13" x 9" baking pan; cover tightly with foil and bake with turkey one hour. Remove foil during last 20 minutes to lightly brown.