Combine the oysters and water; stir and refrigerate at least 1 hour. Strain and reserve the oysters and oyster water; refrigerate until ready to use.
Melt 4 tablespoons of the margarine in a large skillet over high heat. When margarine is almost melted, add 3/4 cup of the onions, 1/2 cup of the celery and 1/2 cup of the bell peppers. Saute over high heat until onions are dark brown but not burned, about 8 minutes, stirring frequently.
When the onions are browned, stir 2 teaspoons of the Bayou Blast and the garlic into the skillet. Reduce heat to medium and continue cooking 5 minutes, stirring occasionally. Add the remaining 3/4 cup onions, 1/2 cup celery, 1/2 cup bell peppers and 1 stick margarine, and 1/4 cup of the green onions, 1/4 cup of the parsley and the bay leaves. Stir until margarine is melted. Continue cooking 10 minutes, stirring occasionally. Stir in the reserved oyster water and cook over high heat about 10 minutes, stirring occasionally. Stir in the remaining 2 teaspoons Bayou Blast and enough bread crumbs to make a moist, but not runny dressing; remove from heat. Stir in the drained oysters. Spoon dressing into an ungreased 8 x 8-inch baking pan and bake uncovered in a 350° oven for 30 minutes. Remove from oven, discard bay leaves and stir in the butter and the remaining 1/4 cup green onions and 1/4 cup parsley.