No oil. Just seasoned salt, orange juice, cilantro sprigs, and slivered onions. I coat the meat first with the seasoning salt, then put it in a ziploc, in between layers of cilantro and onion so each surface of the meat is in contact with the cilantro and onion. Then I pour in the OJ, and as I seal the bag, squeeze as much air out of it as possible. Let it sit at least 24 hours in the fridge. if you have either costco or Sam's club near you, they carry really good USDA Choice skirt steak which is ideal for carne asada. Make sure you slice the meat against the grain...