Oatmeal Raisin Cookies are one of the food items in Greg's cafeteria. They replaced Chocolate Chip Cookies and were the only item Greg used to buy from the cafeteria. Even though they are replaced, he still buys them but while eating he tries his best not to bite into a raisin. Greg has a theory that Oatmeal Raisin Cookies were never meant to be eaten and were just a joke made in the ancient times to fool people into thinking they were Chocolate Chip Cookies. However, the fact is that chocolate chip cookies were actually invented in the 1930s by Ruth Graves Wakerfield when he put chunks of a candy bar into cookies instead of chocolate powder he used.