Cook the barley to package directions, transfer to a large serving bowl and set aside.
For the dressing: In a bowl whisk together the lemon zest, lemon juice, dill and sugar. Whisk in the olive oil until smooth. Season with salt and pepper to taste.
Toss the barley with the salad dressing. Fold in the cucumber, tomato, onion, olives, cheese, mint and pepperoncini. Season with more salt and pepper to taste if desired.
Garnish with more crumbled feta cheese and dill. Serve cold or at room temperature.