Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Cut the chicken breast into 1-inch bite-sized cubes and place them in a large mixing bowl.
Chop the zucchini into half-moons, slice the bell pepper into strips, and break the broccoli into small florets.
In a small jar or bowl, whisk together the olive oil, lemon juice, minced garlic, dried oregano, sea salt, and black pepper.
Add the vegetables to the bowl with the chicken and pour the lemon-herb marinade over the top.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the dressing.
Spread the mixture in a single layer on the prepared baking sheet, ensuring nothing is overcrowded.
Roast for 18-22 minutes, or until the chicken is cooked through and the vegetables are tender and slightly charred.
Remove from the oven and serve immediately while hot.