Combine barley and a pinch of salt in a pot and add water to cover by 2 inches. Bring to a boil over high heat. Reduce heat to medium and simmer uncovered until tender, about 20 minutes. Drain the barley in a colander. Rinse well under cold running water until cool. Drain well.
Combine cooled barley and remaining ingredients plus 1 ½ teaspoons salt in a large serving bowl. Toss to mix well. Taste for seasoning.
Cover and let sit at room temperature for a few hours before serving or cover and refrigerate for up to 2 days.