Combo orders with stock and option legs.

√úbersicht: 

Combo orders which involve a stock and an option leg are accepted natively only at ISE.  So if you would like to create a covered call position, and wish to buy the stock and sell the option simultaneously, ISE is the exchange to which these orders will be sent if, in fact, the specific options trade at the ISE.

Background: 

In the event that the option in question does not trade at ISE, the order can't be sent to that exchange.  These orders will stay on IB's system until the point at which the possibility exists that both legs may be executed simultaneously. 

For example, if you are long XYZ stock and short an XYZ call against it, you might choose to close this position using a combo order.  This order will be sent to ISE since it has a stock and option component.  However, if XYZ options don't trade at ISE, they can't accept the order.  In this case the order will stay on IB's server until the system reads that the XYZ stock can be sold and the XYZ option bought, at which point the system will send the orders simultaneously to the respective exchanges.  Please note that although it is possible that both orders will be executed simultaneously at the combo price, there is no guarantee of fill simply because the displayed quotes from each exchange indicate the combo price is available.