An at the opening order is a market order or limit price order that is to be transacted at the opening of a stock and the corresponding opening price. If the trade doesn't occur at the opening of the stock, then any order or portion of the order that has not been executed is in effect, cancelled. This type of order is currently not offered in the Marketocracy competition. Although you can make a market or limit order on the opening of a stock, it will not be cancelled if it does not fill at the corresponding opening price.