Whisk together the olive oil, lemon zest, lemon juice, harissa, 1 teaspoon salt and 1/4 teaspoon pepper in a large bowl. Add the chickpeas, tomatoes, parsley, feta, olives, celery, celery leaves and onions to the bowl. Toss and check for seasoning. Add more salt and pepper if desired.
From Young Sun Huh for Cooking Channel