Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
In a small mixing bowl, whisk together the harissa paste, extra virgin olive oil, and lemon juice until well combined.
Slice the chicken breast into bite-sized strips and chop the bell pepper, zucchini, and red onion into uniform pieces.
Place the chicken and vegetables in a large bowl, pour the harissa mixture over them, and toss until everything is thoroughly coated.
Spread the mixture in a single layer on the prepared baking sheet, ensuring it is not overcrowded, and season with sea salt and black pepper.
Roast for 20 to 25 minutes, or until the chicken is cooked through and the vegetables are tender with slightly charred edges.
Remove from the oven and sprinkle with freshly chopped parsley before serving.