Preheat the oven to 375°F.
Prepare a baking sheet with parchment paper and set aside.
Clean the Brussels sprouts, cut the stems off, slice in half, and place them into a mixing bowl.
Add the oil, maple syrup, garlic, onion, salt, and pepper to the bowl.
Stir to coat all the Brussels sprouts.
Pour the sprouts onto the baking sheet and spread them out evenly.
Place the baking sheet into the oven and bake for 20 minutes.
After 15 minutes, stir the sprouts and return to the oven for another 15 to 20 minutes.
Remove from the oven when the sprouts are slightly browned and tender.
Serve immediately, as a side dish for any meal.
