In a bowl, start the marinade for the hangar steak by blending the oil, vinegar, garlic, rosemary, salt and pepper blend and lemon juice and whisk together well. Place the steak in an 8 by 12-inch casserole pan and generously coat with the marinade. Allow to marinate for 30 minutes to 1 hour under refrigeration.
For cooking, preheat a grill or chargrill over high heat. Remove the steak from the marinade, straining any excess marinade. Removal of the excess marinade will prevent flaming or charring of the steak during cooking. Place the steak on the grill and cook over high heat, 8 to 9 minutes per side, or to desired doneness.
Remove from the grill and allow the steak to rest before slicing. Slice the steak on the bias, top to bottom, against the grain, 1/4 inches thick. Place the sliced steak over potatoes and serve.