Place hens in a lightly greased 9x13 inch baking dish. Stuff each hen with 1 lemon half and 1/4 of the sliced leeks, then sprinkle with seasoning.
Bake at 350 degrees F 9175 degrees C) for 1 hour, or until hens are cooked through and juices run clear. Let stand 10 minutes, then remove lemon and leeks.