need to cook beef on a spit for 120 people. whats the best cut of beef to use? ideas for a marinade?
I would suggest a Steam Ship Round, maybe two depending on the size of it.
The "Steamship Round" is basically the whole primal Round (Top Round, Bottom Round and Eye Round) with the shank meat removed from the bone and the Sirloin Tip removed. But, that depends on the packer also. It can weigh up to 50-60 lbs, sometimes smaller, depending on the size of the cow.
It's great for 'display' purposes and putting on a show for large groups. It is best slow cooked on a spit, unless you have a large commercial oven available. Most chefs will sit the cooked roast standing up (bone in the air) and slice the meat thin. The tricky part here is that the grain will run in different directions, keeping the carver on his toes. Sliced thin against the grain, the meat will be relatively tender.
Any meat shop should be able to order you one of these from their supplier.
Be tough to marinate, but your favorite BBQ rub and wet mop while it's cooking is suggested. Me? I'd go with the basic Kosher salt, garlic and pepper, not covering up the taste of the meat, while the fat drips and the fire will add some crispness and extra flavor.
If you wanted to spend more money, you could buy several Boneless Top Sirloin Butts.....these can weigh around 10-12 lbs each, but are fairly inexpensive at Sams and or Costco.