Trim fat from meat. Cut meat into 1-inch cubes. In a large skillet brown meat, half at a time, in hot oil. Drain off fat.
Transfer meat to a 3 1/2-, 4-, or 5-quart slow cooker. Stir in leeks, onion, split peas, bay leaves, garlic, dried oregano (if using), cumin, and pepper. Pour chicken broth over all.
Cover and cook on low-heat setting for 8 to 10 hours or on high-heat setting for 4 to 5 hours. If using low-heat setting, turn to high-heat setting. Stir raisins into meat mixture. Cover and cook for 10 minutes more. Discard bay leaves. Stir in lemon juice and if using, the fresh oregano.
To serve, divide the hot bulgur among 6 shallow bowls. Ladle the meat mixture over bulgur.