A type of option order which treats two or more option orders as a package, whereby the execution of any one of the orders causes all the orders to be reduced by the same amount. For example, the investor would enter an OCO order if he/she wished to buy 10 May 60 calls or 10 June 60 calls or any combination of the two which when summed equaled 10 contracts. An OCO order may be either a day order or a GTC order.