Preheat the oven to 200°C (400°F).
Cut the eggplant, bell pepper, and zucchini into even bite-sized pieces.
Arrange the vegetables and cherry tomatoes on a large baking tray.
Nestle the chicken breasts among the vegetables.
Drizzle with olive oil and balsamic vinegar.
Sprinkle with oregano, salt, and pepper.
Squeeze the lemon over everything and place the lemon halves on the tray.
Roast for about 30 minutes, or until the chicken reaches 69°C (160°F). It will continue cooking to 74°C (165°F) while resting.
Meanwhile, cook the orzo in salted boiling water until about 2 minutes shy of the package directions. Drain and rinse under cold water.
Rest the chicken for 5 minutes before slicing.
Toss the sliced chicken with the roasted vegetables, cooked orzo, and all of the flavorful pan juices.
Sprinkle with crumbled feta and drizzle with extra balsamic vinegar if desired before serving.