In small bowl, combine oil, orange juice, garlic, oregano, and salt and pepper. Let stand for 1 hour.
With sharp knife, cut pork lengthwise, exposing the bone. Cut around the bone and remove. Making small cuts, spread meat until flat. Trim into a rectangular shape. Discard any excess fat.
Transfer meat to shallow pan. Coat with marinade and refrigerate for at least 2 hours.
Preheat oven to 375°F.
Spread Moros y Cristianos down the middle of meat and fold to fully cover stuffing. Tie with a string both lengthwise and across. Roast for 20 minutes per pound or until inside cavity reaches 150°F.