Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
In a large mixing bowl, whisk together the harissa paste, extra virgin olive oil, lemon juice, minced garlic, sea salt, and black pepper.
Slice the chicken breast into 1-inch strips and add them to the bowl, tossing until every piece is thoroughly coated in the spicy marinade.
Slice the bell peppers and zucchini into bite-sized pieces and thinly slice the red onion.
Add the prepared vegetables to the bowl with the chicken and toss again to ensure the harissa mixture glazes all the produce.
Spread the chicken and vegetable mixture onto the prepared baking sheet in a single, even layer to ensure proper roasting.
Place in the oven and roast for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables have developed caramelized, charred edges.
Remove from the oven and let rest for 2 minutes before serving hot.