I'd do a deconstructed Turkey.
Saw this on an episode of ATK and had been dying to try it and was really pleased with the results and if I had a bird that big, would not hesitate to do it.
Took a 15lb. brined bird, cut the breasts from the bone, seasoned with Bigmista's Chicken Scratch and wrapped them back in the skin and tied them into a roast. Kept the legs and thighs whole, cooked them in a pan in the BWS Gater at 325-350*
Not much to look at, but slicing the breast was a dream, nice and moist and the dark meat was where its at!