Preheat your oven to 400°F and line a large sheet pan with parchment paper.
Cut the chicken breast into 1-inch strips and chop the bell pepper, zucchini, and red onion into bite-sized pieces.
In a large mixing bowl, whisk together the harissa paste, olive oil, sea salt, and black pepper until well combined.
Add the chicken and vegetables to the bowl, tossing thoroughly to ensure every piece is coated in the spicy marinade.
Spread the mixture in a single, even layer across the prepared sheet pan to ensure proper roasting.
Roast for 20-25 minutes, or until the chicken is cooked through and the vegetables have developed a light char.
Remove from the oven, drizzle with fresh lemon juice, and garnish with chopped parsley before serving.