In large, resealable plastic bag, add vinegar, oil, garlic, oregano, salt, pepper, and steak. Seal bag, pushing out air, and turn to coat steak well. Place on plate and marinate 15 minutes at room temperature.
Preheat grill to medium.
Remove steak from marinade and place on preheated grill. Discard remaining marinade.
Grill steak until desired doneness, about 7-8 minutes per side for medium rare.
Remove steak to serving platter and let rest 10 minutes before slicing.