¼ tsp freshly ground black pepper, plus more to taste
Do ahead: Cook barley according to package instructions until tender (generally, boil for approx 1 hour in a large pot of salted water) Drain cooked barley in colander. Rinse, tossing, with cold water until starchiness is washed off.
In a large mixing bowl, combine remaining ingredients. Stir to combine well. Add rinsed/drained cooked barley. Stir to combine. Add additional kosher salt and pepper as needed. Let salad chill 1-2 hours, covered, for flavors to meld before serving.