1.Spray heated barbecue grill plate with cooking-oil spray for 2 seconds. Cook kumara and zucchini, in batches, until tender. Cool 10 minutes.
2.Meanwhile, combine couscous with stock in large heatproof bowl, cover; stand 5 minutes or until liquid is absorbed, fluffing with fork occasionally.
3.Place ingredients for orange dressing in screw-top jar; shake well.
4.Add kumara, zucchini and remaining ingredients to couscous; stir gently to combine. Serve salad drizzled with dressing.