Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Chop the red bell pepper and zucchini into bite-sized pieces.
Place the broccoli, bell pepper, and zucchini on the baking sheet. Drizzle with half of the olive oil and season with half of the oregano, garlic powder, salt, and pepper. Toss to coat evenly.
Roast the vegetables for 15-18 minutes until tender and slightly caramelized at the edges.
While vegetables roast, season the chicken breast with the remaining oregano, garlic powder, salt, and pepper.
Heat the remaining olive oil in a non-stick skillet over medium-high heat. Add the chicken and cook for 6-7 minutes per side, or until the internal temperature reaches 165°F.
Let the chicken rest for 3 minutes before slicing into strips.
Warm the pre-cooked brown rice and place it in the base of a bowl.
Top the rice with the roasted vegetables and sliced chicken breast.
Drizzle the entire bowl with fresh lemon juice before serving.