1 Grill burgers for 4 minutes without disturbing. 2  Open the barbecue lid, flip the burgers over and cook the opposite side for 3 minutes. 3  Flip the seared burgers twice more over the next 4 to 6 minutes, or until an internal temperature of 135F to 140F is reached. Preheat the barbecue grill or prepare charcoal so that a medium-hot grill surface of 475 to 500F is maintained. 2  Brush some cooking oil on the top side of the burgers. 3  Quickly grease the preheated grill with a rag or paper towel soaked with some cooking oil. 4  Place the burgers on the pre-heated grill, top side down.