Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Slice the chicken breast into even 1-inch bite-sized pieces and halve the baby potatoes.
In a small mixing bowl, whisk together the olive oil, lemon juice, minced garlic, dried oregano, sea salt, and black pepper.
Place the chicken pieces, halved potatoes, and broccoli florets onto the prepared sheet pan.
Pour the lemon-herb dressing over the chicken and vegetables, tossing thoroughly to ensure every piece is well coated.
Spread the ingredients out into a single, even layer so they roast properly rather than steaming.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken is cooked through and the potatoes are fork-tender.
Remove from the oven and serve immediately while the vegetables are crisp and the chicken is juicy.