In a small mixing bowl, whisk the red wine, onions, olive oil, ginger, vinegar, garlic, salt and pepper. Set steaks in a glass bowl and pour ingredients over steaks.
Cover and refrigerate for 8 hours or overnight. Prepare grill to Medium heat.
Remove steaks from marinade. Do not use the marinade and throw away. Position steaks on oiled grill. Grill for 15 minutes. Turn steaks after 8 minutes. To check if done, cut the center with a sharp knife.
To serve, cut flank steak in thin slices across the grain.
Servings: