Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Dice the chicken breast into 1-inch cubes and chop the bell peppers, zucchini, and red onion into similar bite-sized pieces.
In a small mixing bowl, whisk together the extra virgin olive oil, lemon juice, minced garlic, dried oregano, sea salt, and black pepper.
Place the chicken and all the chopped vegetables onto the prepared sheet pan.
Drizzle the lemon-herb dressing over the chicken and vegetables, then toss thoroughly with your hands or tongs to ensure every piece is well-coated.
Spread the mixture out into a single, even layer across the pan to ensure the ingredients roast rather than steam.
Bake for 18 to 22 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 rest for 2 minutes before serving to allow the juices to redistribute.