Preheat oven to 400°F and line a baking sheet with parchment paper.
Season the chicken breast with half of the salt, pepper, and garlic powder, then roast for 20 minutes until cooked through.
Dice the zucchini, bell pepper, and onion, toss them with half of the olive oil, and roast for 15 minutes until tender.
Boil a pot of salted water and cook the orzo according to package directions, then drain and rinse with cold water.
Dice the roasted chicken into bite-sized pieces and place in a large mixing bowl.
Add the cooked orzo, roasted vegetables, lemon juice, remaining olive oil, oregano, and remaining seasonings to the bowl.
Toss everything thoroughly and garnish with fresh chopped parsley before serving.