Preheat your oven to 400°F (200°C). Prepare a large rimmed baking sheet by lining it with parchment paper or greasing it lightly.
In a large mixing bowl, combine olive oil, lemon juice, lemon zest, minced garlic, oregano, thyme, salt, and pepper. Mix well to create a marinade.
Add the chicken breasts to the marinade, ensuring they are fully coated. Let them marinate for at least 15 minutes while you prepare the vegetables.
In another bowl, toss the Brussels sprouts, baby potatoes, and bell peppers with a drizzle of olive oil, salt, and pepper until evenly coated.
Arrange the marinated chicken breasts on one side of the prepared baking sheet. On the other side, spread the seasoned vegetables.
Bake in the preheated oven for 25-30 minutes, or until the chicken is cooked through (internal temperature should reach 165°F or 75°C) and the vegetables are tender and slightly caramelized.
To finish, broil the sheet pan for an additional 2-3 minutes for a golden-brown touch, if desired.
Remove from the oven and let it rest for 5 minutes. Garnish with chopped fresh parsley before serving.