Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Slice the chicken breast into 1-inch bite-sized pieces and place them in a large mixing bowl.
Chop the broccoli into florets, slice the carrots into thin rounds, and quarter the zucchini into half-moons.
Add the prepared vegetables to the bowl with the chicken pieces.
In a small jar or bowl, whisk together the olive oil, lemon juice, minced garlic, dried oregano, sea salt, and black pepper.
Pour the marinade over the chicken and vegetables, tossing thoroughly with your hands or a spatula to ensure every piece is evenly coated.
Spread the mixture in a single layer across the baking sheet, making sure not to overcrowd the pan so the vegetables roast rather than steam.
Roast in the center of 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 caramelized edges.
Remove from the oven and let rest for 2 minutes before serving warm.