In a small bowl, mix the juice of the 3 limes, garlic, dried oregano and olive oil. Rub all over the hens and set in the refrigerator 1 to 2 hours.
Preheat the oven to 375 degrees.
Remove the hens from the refrigerator. Stuff the cavity of each with half of the fresh oregano, a lime half and half of the onion chunks. Tie the legs together with string and sprinkle all over with salt and pepper. Place on a rack in a roasting pan and roast breast side up, 20 minutes. Turn breast side down and roast another 20 minutes. Then turn over again and roast 20 minutes longer (1 hour total). Serve hot.
c.1996, M.S. Milliken & S. Feniger, all rights reserved