1. Sprinkle steak on both sides with pepper and salt. Combine vinegar, olive oil, and garlic in a large heavy-duty zip-top plastic bag. Add steak to bag; seal. Marinate in refrigerator 8 hours, turning occasionally.
2. Prepare grill.
3. Remove steak from bag, discarding marinade. Place steak on a grill rack coated with cooking spray. Grill 6 to 8 minutes or until desired degree of doneness. Remove steak from grill; cover and let stand 5 minutes. Cut diagonally across the grain into thin slices. Serve with Green Olive Tapenade.