Grill on on outdoor barbecue grill or on a stove top cast iron skillet over medium-high heat for appx. 4-6 minutes on each side or until internal temperature reaches at least 155-degrees. Remove from the grill and allow the burgers to rest for about 5 minutes (this allows the beef to continue cooking and reach a temperature of about 160-degrees before eating). We find you can get the best temperature estimate using an instant-read thermometer.