additional rosemary and other herbs, like oregano, thyme, marjoram, etc - to make a basting brush, optional
Instructions
Peel the skins off the garlic cloves and slice them into thin slivers. With a sharp knife, make slits across the lamb and insert the garlic slivers. Repeat, adding as many as you can.
Add the olive oil, lemon juice and fresh rosemary to a durable, sealable plastic bag. Season with salt and pepper. Add the lamb and seal the bag, pressing out air. Turn bag to coat lamb, then put bag in a shallow baking pan and place in the refrigerator to marinate, turning bag over occasionally, overnight or up to 3-days before grilling.
Bring lamb to room temperature, about 1 hour, before grilling. Just before grilling, remove the lamb from the marinate and shake off excess marinade. Pour the marinade into a shallow bowl. If you'd like to get fancy, tie a bunch of sturdy sprigs of fresh herbs together with kitchen twine to make a basting brush (or just use a regular basting brush).
Make sure your grill grates are clean. Heat one side of your grill to a high heat. Place the lamb on the direct heat and sear on all sides. Just about 1-2 minutes per side, until browned. Move the lamb to the unheated side of the grill, and keep the high-heat side on high.
Cook the lamb on indirect heat, turning every 15 minutes to evenly cook on all sides, basting with the marinade as you go. Cook to 120 - 125º for rare, 140-145º for medium-rare, 160º for medium. It may take 40 minutes to 1 hour (or longer), depending on the size of your leg.
Remove from the grill and transfer to a platter, cover with aluminum foil, and allow to rest for 20 minutes. It will continue to heat through as it rests, so be sure not to overcook on the grill.
Then cut across the grain, as slices or into bite-sized chunks/cubes (which is how my dad usually does it) season with sea salt and black pepper. Serve.
Serve with a Greek salad, roast potatoes or Greek Potato Salad, feta, kalamata olives and/or tzatiki all make incredible compliments. Enjoy!
Notes
This marinade amount will work for a roast as large as 5 lbs, no need to adjust. Cook time may increase, however. if you don't have access to an outdoor grill, you can sear and fully cook in a well-seasoned grill pan, cooking for approximately 12-15 minutes per side (or until desired internal temp is reached) or roast the lamb in the oven at 325ºF, quickly searing first in a hot pan over high-heat.