Wash duckling and set aside giblets. Place orange and onion pieces in body cavity of duckling. Secure neck skin flap with toothpicks or wooden skewers.
Tie legs together and tie wings to body. Place duckling, breast side down, on a microwave roasting rack or inverted microwave-proof saucer in a 12 x 7-inch microwave-proof baking dish. Put marmalade in a 1-cup glass measure. Cook on HI (maximum power) for 1 minute. Spread 1/2 of the warm marmalade on duckling. Cook in microwave oven on 70 (roast) for 20 minutes. Remove from oven and drain off excess fat.
Turn breast side up. Brush with remaining marmalade. Cover with waxed paper and cook on 70 (roast) for 15 to 20 minutes, or until meat near bone is no longer pink. Let stand, covered with aluminum foil, 10 minutes before serving.
Servings: 4