Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Slice the chicken breast into even 1-inch strips and place them in a medium mixing bowl.
Chop the red bell pepper, zucchini, and red onion into bite-sized chunks and set aside.
In a small bowl, whisk together the harissa paste, extra virgin olive oil, and lemon juice until smooth.
Pour two-thirds of the harissa mixture over the chicken and the remaining third over the vegetables, tossing both until thoroughly coated.
Spread the chicken and vegetables in a single layer on the prepared baking sheet, ensuring they aren't overcrowded.
Season everything evenly with sea salt and black pepper.
Roast for 18-22 minutes, or until the chicken is cooked through and the vegetables have developed a slight char.
Remove from the oven and garnish with freshly chopped parsley before serving hot.