Add sour cream on top of the nachos after they are done. How Long do you Keep Foil Packets in the Oven? Preheat the oven to 350 degrees. Place the foil packets on a large-rimmed baking sheet.

Layer the nachos up in a high sided baking tray ... and then cover the tin with foil and leave it to bake, either in the oven or over your campfire. All that's left is to tuck in!