Season the steak lightly with salt and pepper. In a resealable plastic bag, combine the olive oil, vinegar, crushed red pepper and parsley. Add the steak to the bag and turn to coat completely with the marinade. Refrigerate, turning occasionally, for at least 6 hours and up to 12 hours.
Remove the steak from the marinade and bring to room temperature.
Light a grill or preheat a grill pan and brush with vegetable oil. Season the steak with salt and pepper and grill over moderately high heat until well-browned outside and medium-rare within, about 3 1/2 minutes per side. Transfer to a carving board and let rest for 5 minutes. Thinly slice the steak against the grain and serve.