2Combine Brussels sprouts, red onion, and garlic in a large bowl. Drizzle balsamic vinegar, olive oil, and maple syrup over the sprouts mixture and toss to coat. Season vegetables with salt and pepper; pour onto a baking sheet.
3Roast vegetable mixture in preheated oven until the sprouts are tender and the sauce thickened, about 40 minutes.
4Transfer vegetables and sauce to a large serving bowl; add walnuts, cranberries, and feta cheese and stir to mix.