Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Dice the chicken breast, red bell pepper, zucchini, and red onion into bite-sized, uniform pieces.
Place the chicken and vegetables on the prepared baking sheet, drizzle with olive oil, and season with sea salt, black pepper, and dried oregano.
Toss everything thoroughly to ensure an even coating of oil and spices, then spread into a single layer.
Roast in the oven for 18-20 minutes, or until the chicken is cooked through and the vegetables are tender with slightly charred edges.
While roasting, ensure your quinoa is cooked and warm.
Place the cooked quinoa in a serving bowl and top with the roasted chicken and vegetable mixture.
Drizzle the fresh lemon juice over the bowl and garnish with crumbled feta cheese before serving.