Mix the cinnamon, nutmeg, orange zest, salt and pepper in with the stout and let the foam settle down.
Pour the marinade in a bag and add the Rib Eye.
Let the Rib Eye marinate overnight and then pull from the marinade an hour before putting it on the grill.
Preheat the Big Green Egg to 700° then add the Rib Eye. Cook for 1 minute then turn 45° and cook for another minute.
Flip the Rib Eye and do the same thing on the on the other side. The cap the BGE (close all the vents starving it of oxygen) and let the Rib Eye roast another 5 minutes for medium rare.
Once the Rib Eye is 130° measured by an instant read thermometer pull the steak and let rest for 10 minutes. Slice and serve!