Yitz, you ask an excellent question. I had to do a little thinking before answering your question and after careful consideration, here is my opinion.
Leg of lamb is generally a tough cut of meat and the traditional method of preparation is braising, i.e. cooking in a covered dish with liquid. That being said, you can grill leg of lamb by butterflying it (cutting it open in a manner as to make it one flat even piece of meat without any bones) and removing any cartilage and connective tissue. You would then marinate the meat (a garlic-herb paste with mint is excellent) and the grill it over medium high heat. Slice it really really thin and it is delicious.
Now that we got that out of the way, the front leg is generally smaller and tougher than the hind leg. So, what I would recommend is to follow the same procedure as outlined above (butterfly the meat, rub with garlic-herb paste and marinate for 48 hours). Then, season the meat well with salt and pepper and cook in a covered baking dish at 300 degrees for about 3 hours or until just tender. Allow to cool. Before serving, get your grill blazing hot and cook the meat until nicely charred on both sides, rotating 90 degrees to get nice grill marks. Slice the meat really thinly and enjoy!
This method will give you mouthwatering tender meat while allowing you to enjoy the smokey grilled flavor.
~ Chef Jack of “Jack’s Gourmet”