Oreos can be kept in the freezer for up to three months, as long as they're packaged well. Some people actually think that Oreos taste better when they've been frozen, and I happen to agree! You'll want to place the set Oreos on a wax paper or parchment paper-lined baking sheet and freeze them first before storing them in freezer bags or an air-tight container. This will ensure the Oreos maintain their freshness.