Prepare and marinate steak by scoring meat and making shallow cuts at 3 cm intervals diagonally across the steak in a diamond pattern. Repeat on second side. Place meat in a plastic bag and set into a shallow dish. For marinade, combine oil, vinegar, garlic, quarter teaspoon salt and quarter teaspoon pepper. Pour over meat. Seal bag. Marinate at room temperature up to 1 hour or in refrigerator up to 24 hours; turn bag occasionally. Grill marinated steak on an uncovered grill directly over medium coals for 6 minutes. Turn and grill to desired doneness allowing 5 to 6 minutes more for rare or 7 to 8 minutes more for medium rare. Continue as above.