Wash fish, cut several slits on top. Line baking pan with aluminum foil. Rub fish inside and out with salt and pepper. Mix olive oil, oregano, lemon juice, salt and pepper, and garlic together.
Place fish in pan with seasoning mixture. Bake at 350° F. Top with lemon slices. Bake fish until brown. Baste with water. Seal fish with foil so no steam escapes.
Allow to steam in its own juices for 20 minutes. Place on platter and serve. Can be eaten hot or cold.Servings: 4