Combine Brussels sprouts, olive oil, grated parmesan, garlic powder, salt and pepper in a large bowl or ziploc bag. Seal and toss until coated evenly.
Place the Brussels sprouts onto a large baking sheet with the cut-side-down touching the pan.
Bake at 425 F for 20-30 minutes or until the Brussels sprouts are lightly crispy and charred on the outside and toasted golden on the bottoms. Some of the loose outer leaves will be extra dark and crispy but they are still good!
Taste and sprinkle with extra garlic powder, salt or pepper if necessary.
Sprinkle shredded parmesan on top and serve!