In a heavy saucepan, bring orange juice and water to a boil; add barley, reduce heat. Cover and cook 35-45 minutes. Remove from heat; let stand 25-30 minutes. Drain; reserve.
In large bowl, combine vinegar and mustard. Whisk in oil to create dressing. Stir in parsley and rosemary. Add reserved warm barley, peppers, and scallions and toss to to coat. Season with salt and pepper , if desired.
Refrigerate. Let stand at least 1 hour before serving.