Cooking a duck in the oven takes around 1 hour and 40 minutes for a fully cooked duck.
Preheat the oven to 425 F and place the duck on the center rack for 15 minutes until it browns lightly and then after 15 minutes turn the oven temperature down to 350 F and then allow the duck to cook for another 1 hour and 25 minutes.
Adjust the cooking time per lb of duck which is 30 minutes per each lb of duck.