Preheat oven to 400°F (200°C) and line two large baking sheets with parchment paper.
In a large bowl, toss the zucchini, bell peppers, red onion, and cherry tomatoes with 2 tablespoons of olive oil, oregano, salt, and pepper.
Spread vegetables on the first baking sheet and place chicken cubes on the second baking sheet seasoned with garlic powder and a pinch of salt.
Roast both sheets in the oven for 20 to 25 minutes until the vegetables are tender and chicken reaches an internal temperature of 165°F (74°C).
While roasting, bring a large pot of salted water to a boil and cook the orzo according to package instructions until al dente.
Drain the orzo and return it to the pot or a large mixing bowl.
Add the roasted vegetables, cooked chicken, remaining 1 tablespoon of olive oil, lemon juice, and chopped parsley to the orzo.
Gently fold in the crumbled feta cheese and serve immediately while warm or refrigerate for meal prep.