Preheat your oven to 400°F (200°C).
Prepare a marinade by combining olive oil, lemon juice, minced garlic, and chopped fresh rosemary.
Coat the chicken breast with the marinade, ensuring even coverage. Let it marinate for at least 15 minutes.
Chop the zucchini, red bell pepper, cherry tomatoes, and red onion into bite-sized pieces. Toss them with a little olive oil, salt, and pepper.
Place the marinated chicken breast on a baking tray and arrange the vegetables around it. Drizzle any remaining marinade over the vegetables.
Roast in the preheated oven for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender with slight caramelization.
While the chicken and vegetables are roasting, prepare the cooked quinoa according to package instructions if not pre-cooked.
Slice the roasted chicken and serve it over a bed of quinoa, adding the roasted vegetables on top.
Finish with an extra squeeze of lemon juice for added brightness, and enjoy your balanced, flavorful bowl.