In a mixing bowl, combine olive oil, orange juice, lime juice, garlic, cumin, oregano, salt, and black pepper to make the mojo marinade.
Place the beef steak in a resealable plastic bag or shallow dish and pour the marinade over it. Seal the bag or cover the dish and refrigerate for at least 2 hours, preferably overnight.
Preheat the grill to medium-high heat. Remove the steak from the marinade and let any excess drip off.
Grill the steak for about 4-5 minutes per side, or until it reaches your desired level of doneness.
Remove the steak from the grill and let it rest for 5 minutes before slicing against the grain.