Market On Open (MOO) is an order type that is submitted to a broker to participate in the market's opening process and be executed at the opening price established by the opening auction. The order does not specify a price and will be filled at the price determined by the opening cross, or canceled if there is no match.
Traders and funds use MOO to align early-day execution with the price discovery that occurs at the open, potentially avoiding large movements that can occur during the pre-market session. The order is typically routed to the exchange's opening session, where it competes with other orders for prints in the opening cross. Depending on liquidity, an MOO order may be fully filled at the opening price, partially filled, or not filled at all.
There is no assurance of a specific price, and the opening price can be volatile as supply and demand balance in the first trades. MOO orders may be canceled if they cannot be matched in the opening auction, or if the broker's venue rules specify.
MOO is one of several opening- and crossing-related order types used in U.S. equity markets; it sits alongside terms such as Market On Close (MOC) and Limit On Open (LOO) that describe different ways to participate in price formation around market hours.
A trader submits an MOO order before the market opens to participate in the opening cross and have the execution occur at the opening price if there is a match.
Market On Close (MOC) · Opening Auction · Limit On Open (LOO) · Opening price · Pre-market trading · Price discovery