3 lb flank steak
1/3 cup white wine vinegar
2/3 cup good olive oil
1 tsp mustard
4 TBS Worcestershire Sauce
2 cloves chopped garlic

Prick the flank steak all over with a fork.  Add the remainder of the ingredients in a large resealable plastic bag. Add the flank steak and marinade for 1~ 4 hours.
Grill flank steak over medium heat for 6 minutes per side for medium rare.

Plate and let rest for 10 minutes. Slice in thin slices against the grain.

Serve with Chimichurri Sauce.