Cook barley according to package directions. Drain, if needed. Set aside to cool.
Mix cooled barley, tomatoes, cucumber, feta cheese, red onion, Kalamata olives, parsley, and oregano. Season to taste with salt and pepper. Add Greek vinaigrette and red wine vinegar to taste, if planning to serve/consume all or most at one meal. If planning to serve/consume over the next few days (re: brown bag), add minimal amounts of dressing and vinegar, then freshen at serving by adding a splash more of each.