Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Dice the chicken breast into 1-inch cubes and chop the sweet potato, broccoli, and zucchini into uniform, bite-sized pieces.
In a large mixing bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Add the chicken and vegetables to the bowl, tossing thoroughly until every piece is evenly coated with the aromatic lemon marinade.
Spread the mixture in a single layer on the prepared sheet pan, ensuring the ingredients aren't crowded so they roast to perfection.
Bake for 20-25 minutes, or until the chicken is cooked through and the sweet potatoes are tender with golden, caramelized edges.
Remove from the oven and finish with an extra squeeze of fresh lemon juice if desired before serving this clean and colorful meal.