How long to cook depends on the cut of beef. Heat the grill to 450 ºF. Add the thin flap steak and grill for 5-6 minutes per side. If using flank steak the cook time is slightly different. Grill 5-6 minutes on each side until it reaches an internal temperature of 130 ºFF for medium rare. 7-8 minutes on each side for medium. Mazola Corn Oil is the best choice for grilling, because it has a high smoke point of 450ºF, whereas other cooking oils like extra virgin olive oil, range between 325-400ºF.