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 halve the baby potatoes to ensure they cook at the same rate as the vegetables.
In a small mixing bowl, whisk together the extra virgin olive oil, lemon juice, lemon zest, dried oregano, garlic powder, sea salt, and black pepper.
Place the chicken cubes, halved potatoes, broccoli florets, and sliced red bell pepper onto the prepared sheet pan.
Drizzle the lemon-herb dressing over the chicken and vegetables, then toss thoroughly with your hands or tongs to ensure every piece is well-coated.
Spread the ingredients out into a single layer, making sure not to overcrowd the pan so the vegetables roast and caramelize rather than steam.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken is cooked through and the potatoes are golden and fork-tender.