Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
In a small mixing bowl, whisk together the extra virgin olive oil, harissa paste, lemon juice, minced garlic, and dried oregano until well combined.
Slice the red bell pepper into strips, the red onion into wedges, and the zucchini into half-moon rounds.
Place the chicken breast on one side of the prepared baking sheet and arrange the vegetables on the other side in a single layer.
Brush the harissa mixture generously over both sides of the chicken and drizzle the remaining sauce over the vegetables, tossing them to ensure they are evenly coated.
Season the entire tray with sea salt and black pepper.
Roast in the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender with slightly charred edges.
Remove from the oven and let the chicken rest for 5 minutes before slicing it into strips.
Serve the sliced chicken alongside the roasted vegetables, drizzling any remaining juices from the pan over the top.