Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into uniform 1-inch cubes to ensure even cooking throughout the roasting process.
In a large mixing bowl, combine the chicken cubes, broccoli florets, bell pepper strips, and red onion wedges.
Drizzle the extra virgin olive oil over the mixture and sprinkle with dried oregano, garlic powder, sea salt, and black pepper.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the oil and spices.
Spread the mixture in a single layer onto the prepared baking sheet, ensuring the pieces are not overcrowded.
Roast in the center of the oven for 18 to 22 minutes, or until the chicken is cooked through and the vegetables are tender with slightly charred edges.
Remove from the oven and drizzle with fresh lemon juice to brighten the flavors before serving hot.