To make the dressing, combine all ingredients in a large salad bowl.Toss the chicken with pesto and balsamic vinegar. Set your grill, grill pan, or skillet to medium-high heat. Grill the chicken until cooked through, about 8-10 minutes. Give it a chop. Bring a large pot of salted water to a boil. Boil the pasta to al dente. Drain. Add the hot orzo to the salad bowl full of dressing. Toss, toss! Add the chicken, feta, tomatoes, cucumbers, olives, peppers, and pepperoncini. Toss, toss! Serve warm or cold. The salad will develop more flavor as it sits.