Number One, Get yourself a meat thermometer!
It has been my experience, since the locally grown bird works for their food, the bird has less fat than ones I have bought before I got into farming, more flavor due to it's diversified diet and when you buy a 20 pound (lb) bird you are getting 20 lbs of bird and not 18 lbs of bird injected with saline water prior to packaging. Finally because of the less fat and liquid, it generally cooks faster (to the tune of almost 2 hours faster). Plan accordingly.
Recipe from Local Harvest.
Bring the bird to room temperature before cooking. (You can get a frozen bird from Fort Clux Farm after November 4th and a fresh one from November 18th through 21st.)
Roast free-range heritage turkeys in a hot oven pre-heated to 425F-450F and cook until an internal thigh temperature of 140F-150F is reached. Don't let the tip of the thermometer touch the bone. (Note: The USDA recommends turkeys be cooked to 160F-180F, but these temperature will dry out a heritage turkey. Heritage birds are much more free of disease and bacteria, unlike commercially raised birds, and do not need extreme temperatures to make them safe for consumption)
Cook any stuffing first and put inside the heritage turkey before roasting. Due to the reduced cooking time, stuffing won't become fully cooked. Alternatively, try adding a quartered orange, apple and/or pear inside the cavity instead of stuffing.
Let the roasted bird rest 10-15 minutes before carving.