Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch bite-sized cubes and place them in a large mixing bowl.
Chop the broccoli into small florets, seed and dice the bell pepper, and slice the zucchini into half-moons.
Add all the chopped vegetables to the bowl with the chicken.
Drizzle the olive oil and lemon juice over the mixture, then sprinkle with oregano, garlic powder, sea salt, and black pepper.
Toss everything thoroughly with your hands or a large spoon until the chicken and vegetables are evenly coated in oil and spices.
Spread the mixture in a single layer on the prepared baking sheet, making sure not to overcrowd the pan so the ingredients roast instead of steam.
Bake for 18 to 22 minutes, or until the chicken is cooked through and the vegetables are tender with slightly browned edges.
Remove from the oven and let rest for 2 minutes before serving to allow the juices to redistribute.