Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Slice the chicken breast into even 1-inch strips to ensure they cook quickly and remain juicy.
Remove the stems and seeds from the mini sweet peppers and slice them into rings; peel and slice the red onion into wedges.
Place the chicken, peppers, and onions on the prepared sheet pan.
Drizzle the extra virgin olive oil over the ingredients 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 oil and spices.
Spread the mixture out into a single layer, ensuring the chicken pieces are not overlapping.
Roast in the oven for 18-22 minutes, or until the chicken is cooked through and the peppers are slightly charred at the edges.
Remove from the oven and garnish with freshly chopped parsley before serving.