Preheat your oven to 400°F (200°C) and line a large rimmed sheet pan with parchment paper for easy cleanup.
Cut the chicken breast into uniform 1-inch cubes and place them in a large mixing bowl.
Chop the broccoli into small florets, slice the bell pepper into strips, and half-moon the zucchini.
In a small jar or bowl, whisk together the olive oil, lemon juice, minced garlic, dried oregano, sea salt, and black pepper.
Add all the vegetables to the bowl with the chicken and pour the lemon-herb dressing over the top.
Toss thoroughly with your hands or a spatula until every piece of chicken and vegetable is well-coated.
Spread the mixture onto the prepared sheet pan in a single even layer, ensuring nothing is overcrowded.
Roast for 18 to 22 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and slightly caramelized.
Remove from the oven and let rest for 5 minutes before serving or portioning into meal prep containers.