1. Rinse chicken, pat dry, and pull off and discard lumps of fat. Put legs in a rimmed 12- by 17-inch pan.
2. In a bowl, mix minced garlic, lemon juice, olive oil, oregano, pepper, and salt. Smear garlic mixture evenly over chicken, then arrange legs, cut side down, in a single layer.
3. Bake in a 375° oven until skin is well browned, about 1 1/2 hours (1 1/4 hours in a convection oven). After 45 minutes, baste chicken with pan juices every 10 to 15 minutes.
4. Transfer chicken to a warm platter. Skim and discard fat from drippings. Add 1/2 cup boiling water to pan, stir to loosen browned bits, and pour sauce into a bowl.
5. Scatter chopped parsley over chicken; garnish with parsley sprigs. Add sauce to taste.