Preheat your oven to 400°F (200°C). Lightly oil a 9x13-inch baking dish.
In the prepared dish, combine the uncooked orzo, chickpeas, chopped bell pepper, halved tomatoes, red onion, and minced garlic. Stir to mix.
Arrange the cubed chicken in a single layer over the orzo and vegetable mixture.
In a medium bowl, whisk together the chicken broth, olive oil, red wine vinegar, Dijon mustard, lemon zest, lemon juice, Italian seasoning, salt, and pepper.
Pour the broth mixture evenly over the chicken and orzo. Stir gently to make sure the orzo is submerged in the liquid.
Cover the dish tightly with aluminum foil and bake for 30 minutes.
Carefully remove the foil. Stir the casserole and return it to the oven, uncovered. Bake for another 10 to 15 minutes, until most of the liquid is absorbed and the orzo is tender.
Confirm the chicken is cooked through by checking that it has reached an internal temperature of 165°F (74°C) on an instant-read thermometer.
Let the casserole rest for 5 minutes before serving. Sprinkle with crumbled feta and fresh parsley.