Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Trim the Brussels sprouts and cut them in half. Peel and thinly slice the red onion.
In a large bowl, combine the Brussels sprouts and red onion with olive oil, salt, and pepper. Toss well to coat.
Spread the vegetables evenly on the prepared baking sheet. Roast in the preheated oven for 20 minutes.
While the vegetables roast, dice the chicken breast into bite-sized pieces. Season lightly with salt and pepper.
Heat a non-stick skillet over medium-high heat and cook the chicken until browned and cooked through, about 5-7 minutes. Remove from heat.
In a small bowl, whisk together the honey and balsamic vinegar to create the glaze.
Once the vegetables are roasted and lightly caramelized, remove from the oven. Drizzle the honey-balsamic glaze over the vegetables and toss gently.
Combine the roasted vegetables with the cooked chicken, mixing thoroughly to ensure even distribution of flavors.
Serve warm and enjoy this balanced dish that's perfect for breakfast, lunch, or dinner.