Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup.
Place the halved baby potatoes on the pan, drizzle with half of the olive oil and a pinch of sea salt, then roast for 12 minutes to give them a head start.
While the potatoes are roasting, chop the chicken breast into 1-inch bite-sized pieces and cut the broccoli and red bell pepper.
Remove the pan from the oven and add the chicken, broccoli florets, and sliced bell peppers to the space around the potatoes.
Drizzle the remaining olive oil, fresh lemon juice, lemon zest, dried oregano, garlic powder, sea salt, and black pepper over everything.
Use a spatula or clean hands to toss all the ingredients directly on the pan until they are evenly coated in the lemon-herb mixture.
Spread everything out into a single layer and return the pan to the oven for 15-18 minutes until the chicken is cooked through and the vegetables are tender.