Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper for easy cleanup.
In a large bowl, combine the chicken pieces, broccoli florets, red and yellow bell peppers, and red onion wedges.
In a small bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, oregano, thyme, rosemary, salt, and pepper. Pour this mixture over the chicken and vegetables in the large bowl. Toss everything gently until well coated.
Spread the coated chicken and vegetables in a single, even layer on the prepared baking sheet. Avoid overcrowding the pan, as this will steam the ingredients instead of roasting them. Use two pans if necessary.
Bake for 20-25 minutes, or until the chicken is cooked through (internal temperature reaches 165°F or 74°C) and the vegetables are tender and slightly caramelized. For extra browning, you can broil for the last 1-2 minutes, watching carefully to prevent burning.
Remove from the oven. Garnish with fresh parsley if desired. Serve immediately.