1. Whisk together vinegar, oil, garlic, rosemary and pepper. Poke the beef on both sides all over with a fork. Place beef and marinade in a plastic zipper bag and marinate in refrigerator overnight.
2. Preheat Broiler or grill.
3. Remove beef from bag, pat dry and let sit while grill or broiler is preheating.Sprinkle with salt and pepper to taste.
4. Grill beef over medium - high heat for about 6 minutes per side (for 1" thick).
5. Cover loosely with foil and let rest 10 minutes. Cut against the grain in thin slices.
Recipe created by Heather Quintana, Certified Health Coach