Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Chop the red bell pepper, zucchini, and red onion into uniform bite-sized pieces.
Mince the garlic cloves finely.
In a large mixing bowl, whisk together the harissa paste, extra virgin olive oil, lemon juice, minced garlic, sea salt, and black pepper.
Slice the chicken breast into 1-inch thick strips to ensure even cooking.
Add the chicken strips and the chopped vegetables to the bowl with the harissa mixture and toss thoroughly until everything is well-coated.
Spread the chicken and vegetables in a single layer on the prepared baking sheet, ensuring they are not overcrowded.
Roast for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender with slightly charred edges.
Remove from the oven and let the chicken rest for 3 minutes before serving to keep it juicy.