1. In a mixing bowl, combine soy sauce, olive oil, red wine vinegar, minced garlic, and black pepper.
2. Place the flank steak in a resealable plastic bag and pour the marinade over the steak. Seal the bag and refrigerate for at least 2 hours, or overnight for best results.
3. Preheat the grill to medium-high heat. Remove the steak from the marinade and discard the marinade.
4. Grill the steak for 5-7 minutes on each side, or until desired doneness is reached.
5. Let the steak rest for 5 minutes before slicing against the grain. Serve and enjoy!