One of the biggest obstacles in the wide-spread industrial take-up of grid technology is the existence of a large amount of legacy code that is not accessible as grid services. The paper describes a new approach (GEMLCA: grid execution management for legacy code architecture) to deploy legacy codes as grid services without modifying the original code. Moreover, we show a workflow execution oriented grid portal technology (P-GRADE portal) by which such legacy code based grid services can be applied in complex business processes. GEMLCA has been implemented as GT-3 services but can be easily ported into the new WSRF grid standards.