Simmer the barley in 1 litre water for 45 minutes, or until tender. Drain and set aside to cool. Meanwhile combine all the marinade ingredients and rub evenly over the steaks. Leave to marinate for 1-2 hours.
Blend all the dressing ingredients together and season.
When the steak is ready, get a griddle pan smoking hot. Rub the steaks with oil and lay on the griddle. The meat only needs about 30 seconds on each side. Season with salt as the sirloin is turned. Set aside to rest for a minute.
Meanwhile, put the barley, parsley leaves and grapes in a bowl, add the dressing and mix well. Taste and adjust the seasoning.
Slice the steak into 1cm thick slices across the grain. Toss half with the salad and lay the rest of the strips on top. Serve immediately.