Market on Open Order (MOO)¶
A market on open order (MOO) is an order type that executes at the opening auction price of a stock's primary exchange, guaranteeing a fill at the single price that clears the most shares when the regular session begins at 9:30 AM ET. The order provides certainty of execution but not certainty of price. It is distinct from a standard market order, which routes to the continuous market after the auction.
HOW IT WORKS¶
MOO orders are submitted before the exchange cutoff, typically 9:28 AM ET for NYSE and Nasdaq. The exchange collects all MOO orders, limit on open orders, and market maker quotes beginning at 4:00 AM ET, then calculates the opening price that maximizes matched volume at 9:30 AM ET. Every MOO order fills at that single official opening price. If the stock does not open due to a halt or severe imbalance, the MOO order may be rejected or rolled into the continuous market. The order is not eligible for pre-market execution.
IN TAPEBOARD¶
In the Tapeboard terminal, MOO orders appear in the order entry panel under the Auction order type category. Tapeboard timestamps MOO submissions and alerts you if your entry is within two minutes of the 9:28 AM ET cutoff. The order blotter displays MOO fills tagged with the [MOO] label alongside the official opening print, making it straightforward to compare your fill against the opening auction price and any pre-market reference levels. Tapeboard's opening auction imbalance feed can be used alongside MOO orders to assess directional pressure before submitting.