Abstract: A method and system are provided for obtaining and matching single leg and multi-leg orders to trade combinations of financial instruments included in a set of two or more selected financial instruments. In preferred embodiments, orders are received during a selected time period and eligible orders are processed with a combinatorial matching algorithm that is not constrained by limit prices. All embodiments have the advantages that matched multi-leg orders can be executed with no bid/offer spread on any of their legs, there is no risk that some legs of a multi-leg order execute while others do not execute, and said embodiments can be implemented by selecting two or more existing financial instruments without requiring the creation of any special financial instrument representing a multi-leg strategy.