Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup.
Dice the chicken breast and sweet potato into small, toddler-friendly half-inch cubes, and chop the broccoli and peppers into similar sizes.
In a small bowl, whisk together the olive oil, lemon juice, oregano, garlic powder, salt, and pepper to create the marinade.
Place the chicken and all the vegetables on the sheet pan, drizzle with the marinade, and toss thoroughly to coat every piece.
Spread the mixture into a single even layer, ensuring there is space between items so they roast rather than steam.
Bake for 20 to 25 minutes until the chicken is cooked through and the sweet potatoes are tender when pierced with a fork.
Allow the pan to rest for 5 minutes before serving to let the juices redistribute, making the chicken extra tender for little ones.