the oven MUST have a closed top to cook safely and efficiently.

If it is thawed, you can cut it in half along the backbone and layer it in.

Or, you can cook ahead in the oven and reheat, using the directions in the holiday cooking section at the top of Big Pots. No carving, and it actually makes the meal simpler to serve.

Or you can use a very large rimmed baking sheet in the oven, and just siphon off any extra juices with a turkey baster,

Or you can buy a larger roasting pan and do it in the oven.

Or you can leave it in the freezer and try a different store for a smaller one. Somebody has a 17-18 pound turkey.