Preheat oven to 325F. Stack 2 heavy-duty foil sheets on large baking sheet. Place fish on foil. Sprinkle half of green onions and 2 1/2 tablespoons lemon juice inside fish. Drizzle remaining 2 1/2 tablespoons lemon juice over fish. Drizzle oil over. Pour wine over; sprinkle with peppercorns. Sprinkle remaining green onions around fish. Bring up foil around fish, sealing tightly but leaving airspace between fish and foil. Bake fish 1 hour. Remove from oven. Open foil and let fish cool 1 hour. Reseal foil and refrigerate until cold, about 4 hours. (Can be prepared 1 day ahead. Keep refrigerated.) Open foil. Carefully remove skin from fish. Scrape off any grayish flesh. Transfer fish to platter. Garnish top of fish with cucumber slices. Surround with lemon wedges and dill sprigs. Serves 8. Bon Appetit May 1993