You cannot prepare the entire dish in advance, but you can mix the breadcrumb mixture up to 24 hours in advance and keep it stored in an airtight container in the refrigerator. You can also add the fish to the oiled baking dish up to 12 hours in advance, covered tightly with plastic wrap and refrigerated until ready to cook. Do NOT season the fish or add the lemon juice or white wine in advance, or they will break down the proteins in the fish and make it mushy.