Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Pat the chicken breast dry with a paper towel and cut it into 1-inch bite-sized pieces.
Peel the sweet potato and dice into 1/2-inch cubes, then chop the broccoli into bite-sized florets.
In a large bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Add the chicken, sweet potato, and broccoli to the bowl and toss thoroughly until every piece is evenly coated in the marinade.
Spread the mixture in a single layer on the prepared sheet pan, ensuring nothing is overcrowded so the vegetables roast instead of steam.
Bake for 20-25 minutes, tossing halfway through, until the chicken is cooked through and the sweet potatoes are fork-tender.
Garnish with fresh parsley and store in airtight containers for a meal-prep lunch that reheats beautifully.