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 pieces and chop the zucchini, bell pepper, and broccoli into bite-sized chunks.
Place the chicken and all the vegetables onto the prepared sheet pan.
Drizzle with the olive oil and sprinkle evenly with garlic powder, dried oregano, sea salt, and black pepper.
Toss everything together with your hands or tongs until the chicken and vegetables are lightly coated in oil and spices.
Spread the mixture out into a single layer, ensuring the pieces aren't too crowded so they roast rather than steam.
Roast in the center of the oven for 18 to 22 minutes, or until the chicken is opaque and cooked through and the vegetables are tender.
Remove from the oven and immediately drizzle the fresh lemon juice over the hot chicken and vegetables.
Transfer everything to a large bowl and garnish with the freshly chopped parsley before serving.