Marinate at room temperature for 24 hours, turning every few hours. Just before cooking, remove meat from marinade; drain marinade and SAVE garlic and onions from marinade mixture.
Broil about 4 inches from heat for 20 minutes.
Turn meat, baste with marinade and broil 10 minutes.
Cover lamb with onion and garlic mix and broil another 5 minutes.
Serve with Avgolemono Sauce, below.