How to Cook Brats in Oven. Before you take the bratwurst out of the freezer or refrigerator, make sure to preheat the oven. Line a baking sheet with aluminum foil, and place a wire rack on top. Bake your sheet pan brats and potatoes dinner at 425 degrees for 20-25 minutes, turn the brats and stir/turn the vegetables. Continue to cook for an additional 20-30 minutes or until the brats are golden brown and the vegetables are roasted. Preheat oven to 425 degrees F (220 degrees C). Healthy, crispy, and well-cooked final products make it a winner or close runner-up— and it is certainly one of the best ways to cook brats! The oven is arguably the best way to cook any meal. It is best served straight from the oven… Toss the brown sugar and cayenne pepper together in a large bowl and set aside. Line a baking sheet with aluminum foil and place a wire rack on top. Remove the bratwurst from the beer, and allow to cool to room temperature. Preheat oven to 425°.