Preheat oven to 375 degrees F.
Open the leg of lamb and season the inside with half the garlic, half the thyme leaves, 1 tablespoon olive oil, salt, and pepper. Tie the lamb closed with string. Place it in a roasting pan, season with salt and pepper, and brush it with olive oil. In a bowl mix the beer
, remaining garlic and thyme
, juniper berries, and bay leaves
. Pour this over the lamb and put the roasting pan into oven. Immediately turn the oven down to 325 degrees F. Baste
every 10 minutes. Cook 12 to 13 minutes per pound for medium rare or until internal temperature reaches 130 to 135 degrees F. Remove the roast
from the oven, cover it loosely with foil and allow it to rest for about 10 minutes before carving. Serve with pan drippings