Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Dice the chicken breast into 1-inch cubes and chop the zucchini, broccoli, and bell pepper into uniform, bite-sized pieces.
In a large mixing bowl, whisk together the extra virgin olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Add the chicken and chopped vegetables to the bowl, tossing thoroughly to ensure every piece is well-coated in the lemon-herb marinade.
Spread the mixture in a single, even layer across the prepared baking sheet, making sure not to overcrowd the pan so the ingredients roast instead of steam.
Roast for 20 to 25 minutes, tossing halfway through, until the chicken is cooked through and the vegetables are tender with slightly charred, crispy edges.