Market-On-Open Order (MOO)

Orders that are executed as the market opens, or very shortly after, at the day’s opening price

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What is a Market-on-Open Order (MOO)?

A market-on-open (MOO) order is used to execute a trade when the market opens, or very shortly after, at the day’s opening price. For MOO orders, the share price for the trade must be equal to the opening price recorded that morning. Market-on-open orders are not made with a limit; instead, they are “non-limit” or market orders, meaning they will try to be fulfilled as soon as possible when the security opens for trading.

Market-On-Open Order (MOO)

All market-on-open orders are evaluated before the morning of trading as they can stimulate the market before opening by generating buy/sell imbalances. It creates liquidity issues for a specific security because of the inability to match the number of buy orders to the number of sell orders. In some cases, market makers can temporarily bring in reserve stock to increase liquidity until trading comes back to an even level. More extreme cases can result in the halt of trading until the buy/sell orders can be balanced.

Market-on-open orders must be placed between 7:00 a.m. and 9:28 a.m. EST from Monday to Friday. Provided the imbalance explained above is not present, the orders are definite. The two-minute period (9:28 a.m.-9:30 a.m.) is used for market makers or specialists to determine if the imbalance above is present, based on the orders in queue and their nature. The price and subsequent trades will adjust based on such factors until the opening price is found at 9:30 a.m.

The opening price can vary drastically based on the amount of MOO orders that are present each morning. If there are a significant amount of MOO buy orders, then the opening price can be significantly higher than the previous day’s closing price.


  • A market-on-open order is executed on the market open at whatever the specified price is from the market makers.
  • MOO orders can capitalize on the expected fluctuation of stock prices that day. Additionally, they are definite or guaranteed orders, assuming there is adequate liquidity for the stock based on the balance of buy and sell orders received that morning.
  • There is an additional risk on the trader from MOO orders due to the lack of limit and non-guaranteed opening price. 

Limit-on-Open Order (LOO)

To counter the risk of the day’s opening price being much higher or lower than the previous day’s close, investors can use limit-on-open (LOO) orders. A LOO order is similar to a MOO order because it is only used at market open and does not stay active for the entirety of the trading day.

However, as the name states, a limit-on-open order comes with limit conditions chosen by the investor. The conditions make sure the security is not purchased or sold if the opening price does not meet the investor’s wishes.

Market-on-Close Order (MOC)

Market-on-close orders are a sister order type to MOO. It is not subject to any limits, similar to market-on-open; however, MOC orders are executed at or as close as possible to the market close time and price. It allows investors to purchase stock at a price as close to the end of the day as possible. Market-on-close orders include the risk of end-of-day price swings, and MOC orders cannot be used in all of the financial markets.

Uses and Advantages of Market-On-Open Orders

Market-on-open orders are used when buyers or sellers expect a stock’s price to fluctuate in a favorable direction when the market opens. Many situations, including news releases, quarterly earnings reports, and global events, can happen during market close and lead potential investors to believe that stock prices will fluctuate the next day.

Disadvantages of Market-On-Open Orders

When placing a market-on-open order, the buyer or seller does not know the price that the security will be at market open because it will fluctuate based on the demand and supply of trades that morning.

For example, a broker who wants to purchase a stock at $50 using a MOO order can end up paying much more than they expected. Alternatively, a broker who wants to sell at $50 using a MOO order can end up selling at a much lower price. These are both negative consequences of market-on-open orders because they lack any limits.

Practical Examples

Consider a time when a trader wants to buy 100 shares of Beta Company stock. Suppose there is reason to believe the stock will fluctuate positively after market open based on expected or public information. In such a case, the trader can use a market-on-open order to purchase the 100 shares to capitalize on the expected gain.

In a similar situation, a trader can sell the same 100 shares of Beta Company stock. If they expect the market price to drop substantially after opening based on expected or released information, a MOO sell order can be used to mitigate the loss from the expected drop in stock price.

More Resources

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