To prepare dressing, combine first 5 ingredients in a medium bowl, stirring with a whisk until blended; set aside.
To prepare salad, cook barley according to package directions, omitting salt and fat. Combine cooked barley, bell pepper, red onion, and the remaining ingredients in a large bowl, tossing well to combine. Add the dressing, and toss gently to coat evenly. Let stand 15 minutes.