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 cubes and chop the broccoli, bell pepper, and zucchini into uniform bite-sized pieces.
In a small glass jar or bowl, whisk together the olive oil, lemon juice, minced garlic, dried oregano, sea salt, and black pepper until well emulsified.
Place the chicken and chopped vegetables onto the prepared baking sheet and pour the lemon-herb dressing over them.
Toss everything thoroughly with your hands or tongs to ensure every piece is coated, then spread into a single layer so nothing is crowded.
Roast for 20 to 25 minutes, tossing halfway through, until the chicken is cooked through and the vegetables are tender with slightly charred edges.
Remove from the oven and serve immediately while hot, adding an extra squeeze of lemon if desired.