Prepare Chimichurri Sauce. Place garlic in food processor container. Cover; process until finely chopped. Add remaining sauce ingredients. Cover; process until well blended. Remove and refrigerate 1/4 cup sauce for serving. Place steaks and remaining sauce in food-safe plastic bag; turn steaks to coat. Close bag securely and marinate in refrigerator 15 minutes to 2 hours.
Remove steaks from marinade; discard marinade. Place steaks on grill over medium, ash-covered coals. Grill, covered, 12 to 15 minutes (over medium heat on preheated gas grill, covered, 10 to 13 minutes) for medium rare to medium doneness, turning occasionally.