Abstract: A method for stock and index option trading includes the steps of receiving an option order copy from an order flow provider. The option order is contemporaneously submitted to a market. The option order identifies, as examples, contract elements including a contract identifier, underlying security, strike price, expiry, and option quantity. The method then determines a potential cross quantity and price based on the option order. Subsequently, the method submits a contra-order (with respect to the originally received option order) specifying contract elements including the contract identifier, underlying security, strike price, and expiry, as well as the potential cross quantity and price to the market for fulfillment.