Preheat oven to 375°. Place soup mix in a bowl; add boiling water and let stand for 5 minutes. In a Dutch oven, melt butter. Stir in bread cubes and onion soup mixture. Cover and cook over low heat for 5 minutes, stirring occasionally. Gently stir in the oysters, sausage, parsley and poultry seasoning. , Transfer to a large greased cast-iron skillet or 2-1/2-qt. baking dish. Cover and bake until heated through, 40-50 minutes.