Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into even 1-inch cubes to ensure they cook at the same rate as the vegetables.
In a large mixing bowl, whisk together the extra virgin olive oil, lemon juice, lemon zest, minced garlic, dried oregano, sea salt, and black pepper.
Add the chicken cubes, broccoli florets, sliced carrots, and red onion wedges to the bowl and toss thoroughly until everything is evenly coated in the marinade.
Spread the mixture in a single layer on the prepared baking sheet, ensuring there is enough space between pieces so they roast rather than steam.
Roast for 18 to 22 minutes, or until the chicken is cooked through and the vegetables are tender with slightly caramelized edges.
Remove from the oven and serve immediately, perhaps with an extra squeeze of fresh lemon for added brightness.