In a small bowl, whisk together lemon juice, chopped red onion, chopped oregano, minced garlic clove, salt, pepper and sugar. Slowly whisk in olive oil.
In a large serving bowl, combine hearts of romaine, cucumber, cherry tomatoes, chickpeas, chopped parsley,kalamata olives and feta cheese. Drizzle with dressing and toss well to coat; serve immediately.