Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper.
Cut the chicken breast into 1-inch bite-sized pieces and place them in a large mixing bowl.
Slice the red bell pepper, zucchini, and red onion into uniform chunks and add them to the bowl with the chicken.
In a small ramekin, whisk together the harissa paste, extra virgin olive oil, lemon juice, sea salt, and black pepper.
Pour the harissa mixture over the chicken and vegetables, tossing thoroughly until everything is evenly coated in the spice.
Spread the mixture in a single layer on the prepared sheet pan, ensuring nothing is overcrowded to allow for proper browning.
Roast in the oven 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 garnish with freshly chopped parsley before serving hot.