In a large saucepan of salted boiling water, cook the barley over moderate heat until slightly tender, about 30 minutes. Drain and quickly rinse the barley under running water to cool it slightly. Shake off all the water and transfer the barley to a large bowl.
Cut the grilled vegetables into bite-size pieces and add to the barley. Add the walnut dressing, lemon juice and chives and season with salt and pepper. Garnish with the shaved pecorino cheese and serve warm.