My wife purchased some Longhorn beef from a friend of hers at work. We received some ground beef and we cooked some Longhorn burgers this evening.
The preparation was very easy for the burgers. A little onion powder, a little garlic powder, some worchestershire sauce, a little salt and some fresh pepper. Each patty weighed in at about 1/2 pound. In short, they were very generous in size. The other thing I noticed was how lean the beef was.
I heated the grill to about 425 degrees and oiled it so that the burgers wouldn't stick. I placed the burgers on the grill and seared both sides. As a reminder, do not press down on the burgers with your spatula.
As for the temperature, I would recommend that you cook until the burger is medium rare. Since we knew the source of the beef and the butcher, cooking it to medium rare is just fine and the burger are perfect and juicy.
For more information on the dietary benefits of Longhorn beef, click here.