Preheat your oven to 425°F and line a large baking sheet with parchment paper.
In a small bowl, whisk together the harissa paste, olive oil, lemon juice, sea salt, and black pepper to create the marinade.
Place the chicken breast, sliced bell peppers, sliced zucchini, and red onion wedges on the prepared baking sheet.
Drizzle the harissa mixture over the chicken and vegetables, tossing thoroughly to ensure everything is evenly coated.
Arrange the chicken in the center of the tray and spread the vegetables in a single layer around it for even roasting.
Roast for 20-25 minutes until the chicken reaches an internal temperature of 165°F and the vegetables are tender with slightly charred edges.
Let the chicken rest for 5 minutes before slicing into strips, then garnish the entire dish with fresh parsley and serve.