Place rinsed quinoa in a small heavy based saucepan with 3/4 cup cold water. Cover and bring to the boil, then reduce heat and simmer quinoa until the liquid is absorbed, about 15 minutes. Place Israeli couscous into a saucepan of boiling salted water, reduce heat and simmer for 10 minutes, until soft but still retains some bite. Drain and rinse under cold water. Set both aside.
Heat barbecue grill until hot. Rub corn cobs with a dash of oil and season. Place on the hot grill and cook for 15 minutes, turning regularly. Set aside to cool a little, then stand cob on one end and using a sharp knife cut down to remove kernels. Brush barbecue grill with a dash of oil and place on zucchini. Cook until just tender. Season and set aside with corn kernels.
Place all ingredients in a small screw-top jar, season and shake well.
Rub steaks with a little oil, season and place on a hot barbecue grill. Grill for 3-4 minutes on each side for medium-rare. Remove from grill, cover and set aside to rest.
Place cooked quinoa and Israeli couscous in a large bowl, and using a fork, stir through the corn kernels, zucchini and spinach leaves. Pour over dressing, toss gently and place on a serving plate. Slice sirloin steak and place on top of the grain salad and sprinkle with the sesame seeds, shredded mint and nuts if using. Pass a bowl of rocket aioli (see tips & tricks).
Recipe from recipes.co.nz