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 pieces and place them into a large mixing bowl.
Chop the broccoli florets, red bell pepper, and zucchini into uniform pieces and add them to the bowl with the chicken.
In a small jar or bowl, whisk together the olive oil, lemon juice, minced garlic, dried oregano, sea salt, and black pepper until well combined.
Pour the lemon-herb marinade over the chicken and vegetables, tossing thoroughly to ensure every piece is evenly coated.
Spread the mixture in a single layer across the prepared baking sheet, making sure not to overcrowd the pan so the vegetables roast rather than steam.
Roast in the center of the oven for 18-22 minutes, or until the chicken is cooked through and the vegetables are tender with slightly caramelized edges.
Remove from the oven and serve immediately, garnishing with extra fresh herbs or a squeeze of lemon if desired.