Oreo is giving away a million bars for National Oreo Day

Fans of Oreos can snag a free treat Tuesday, which is National Oreo Day.

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Oreo is giving away a million free Oreo chocolate candy bars. The first million to register on Oreo's website will receive a coupon for a free candy bar. The giveaway ends Monday, or after a million participants have been registered.

NBA legend Shaquille O'Neal is celebrating his birthday by promoting the Oreo giveaway.

The famous cookie was created by the National Biscuit Co. in 1912.