Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Dice the chicken breast into uniform 1-inch cubes to ensure even cooking.
Chop the bell peppers and zucchini into bite-sized pieces, and slice the red onion into thin wedges.
Place the chicken and all the chopped vegetables onto the prepared baking sheet.
Drizzle the extra virgin olive oil over the mixture, then sprinkle evenly with garlic powder, dried oregano, sea salt, and black pepper.
Use your hands or a spatula to toss everything together until the chicken and vegetables are thoroughly and evenly coated in the oil and spices.
Spread the mixture out into a single layer, ensuring nothing is overcrowded so the vegetables roast rather than steam.
Roast in the center of the oven for 20-25 minutes, or until the chicken is cooked through and the vegetables are tender with slightly caramelized edges.
Remove from the oven and let it cool slightly before transferring to airtight glass containers for your 3-day meal prep.