Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
In a small mixing bowl, whisk together the harissa paste, extra virgin olive oil, lemon juice, garlic powder, sea salt, and black pepper until well combined.
Place the chicken breast on one side of the prepared baking sheet and arrange the sliced bell peppers, zucchini, and red onion on the other side.
Brush the harissa marinade generously over the chicken and drizzle the remaining portion over the vegetables, tossing them gently to ensure an even coating.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender with charred edges.
Remove from the oven and allow the chicken to rest for 5 minutes to lock in the juices before slicing it into strips.
Serve the sliced chicken alongside the roasted vegetables, drizzling any pan juices over the top for extra flavor.