Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch cubes and chop the broccoli, bell pepper, and zucchini into bite-sized pieces.
In a small mixing bowl, whisk together the olive oil, fresh lemon juice, minced garlic, oregano, sea salt, and black pepper.
Place the chicken and all the vegetables onto the prepared baking sheet.
Pour the lemon-herb dressing over the chicken and vegetables, tossing thoroughly with your hands or tongs to ensure every piece is evenly coated.
Spread the mixture out into a single, even layer so the ingredients roast rather than steam.
Bake for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender with slightly caramelized edges.
Remove from the oven and let rest for 2 minutes before serving to keep the chicken juicy.