I tested this recipe five times, and every time I had a slightly different roasting time. That is why it is important to have a digital thermometer to check the internal temperature of the turkey meat to ensure it is completely cooked through. For an unstuffed turkey, without basting, it takes plus or minus 3 hours for a 15 pound pastured turkey using high heat for the first hour and medium-high heat for the remaining time. Pastured turkeys tend to have larger more dense breasts and can take more than an hour longer than a conventional turkey of equal weight. Furthermore, if you choose to either baste your turkey or stuff it, the turkey will take even longer. To time your meal, plan to pull the turkey out (step 3) about 5 1/2 hours before you want to serve the meal. If your turkey is done earlier, you can let it rest longer.