Oreo O’s (Post, 1998)
In 1998, Post and Kraft entered into a partnership to create Oreo O’s, a breakfast cereal. The Os did indeed taste like Oreo cookies. A variation of this cereal was called Extreme Creme Taste Oreo Os which contained the Oreo filling in the form of flavored marshmallow.
By 2007, the cereal was discontinued everywhere outside of South Korea. The reason for this was that Post and Kraft are no longer co-branding. (Post owned the rights to the cereal but Kraft owns the Oreo name.) They were able to still produce the cereal in South Korea because the Korean company was eventually acquired by Kraft.
If you miss this delicious cereal, boxes are available for international purchase via eBay.