Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Slice the chicken breast into 1-inch thick strips and chop the bell pepper, zucchini, and red onion into uniform bite-sized pieces.
In a large mixing bowl, whisk together the olive oil, harissa paste, lemon juice, sea salt, and black pepper until smooth.
Add the chicken strips and chopped vegetables to the bowl, tossing thoroughly to ensure every piece is well-coated in the spicy glaze.
Spread the mixture in a single layer across the prepared baking sheet, leaving space between items to allow for proper roasting rather than steaming.
Roast for 18 to 22 minutes until the chicken is cooked through and the vegetables have developed slightly charred, caramelized edges.
Remove from the oven and garnish with freshly chopped parsley for a pop of brightness before serving.