Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Halve the baby potatoes and cut the broccoli into bite-sized florets, ensuring they are uniform for even cooking.
In a small mixing bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper to create the marinade.
Place the chicken breast, halved potatoes, and broccoli florets on the prepared baking sheet.
Drizzle the lemon-herb marinade over the chicken and vegetables, tossing them thoroughly to ensure every piece is well-coated.
Roast in the center of the oven for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the potatoes are golden and tender.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep it juicy, then serve immediately with the roasted vegetables.