Bring 3 cups (750 mL) salted water to a boil. Add barley to pot, reduce to a simmer. Cover and cook 30 min., or until barley is tender. Drain off excess liquid.
Meanwhile grill zucchini 2 to 3 min. on barbecue, preheated to medium-high heat, until tender and grill-marked. Remove from grill, chop into bite-size pieces.
Transfer zucchini to large bowl along with tomatoes, olives and parsley.
In separate small bowl, whisk together Lemon Dressing ingredients.
Fold dressing and feta cheese into barley mixture.