Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into bite-sized 1-inch cubes and slice the zucchini, bell peppers, and red onion into similar-sized pieces.
Place the chicken and vegetables on the prepared baking sheet, then drizzle with olive oil and sprinkle with dried oregano, garlic powder, sea salt, and black pepper.
Toss everything thoroughly with your hands or tongs until the chicken and vegetables are evenly coated in the oil and seasonings.
Spread the mixture into a single layer, ensuring the pieces aren't overcrowded so they roast rather than steam.
Roast in the oven for 18 to 20 minutes, or until the chicken is cooked through and the vegetables are tender and slightly caramelized.
Remove from the oven and transfer to a plate to enjoy as a high-protein, savory snack.