Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch bite-sized pieces and peel and cube the sweet potatoes into 1/2-inch pieces.
In a large mixing bowl, combine the chicken, sweet potatoes, broccoli florets, sliced bell peppers, and red onion.
Drizzle the olive oil and lemon juice over the mixture, then sprinkle with sea salt, black pepper, garlic powder, and dried oregano.
Toss everything together until the chicken and vegetables are thoroughly and evenly coated with the oil and seasonings.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the pieces are not overlapping so they roast properly.
Bake for 20 to 25 minutes until the chicken is cooked through and the vegetables are tender and slightly caramelized.
Allow the medley to cool slightly before dividing it into three equal portions in airtight containers for your 3-day meal prep.