To best exploit the potential of the Grid, it is necessary to "Grid-enable" legacy applications that were not originally developed to run on a Grid. In this paper, a generic framework to Grid-enable legacy applications is presented. In particular, this paper focuses on a general approach to model and represent an application in a way that is supportive of the key properties of the Grid-enabling framework: generality, automatic generation and integration of Grid applications, plug-and-play deployment, and interoperability. Based on the model, a configuration language is developed to describe a wide range of command-line applications and their execution requirements. It is easy to use and does not require the application enabler to know the details of the Grid middleware. A case study is presented to illustrate the automated Grid-enabling of a legacy application in In-VIGO (In-Virtual Information Grid Organizations), a Grid computing infrastructure that makes extensive use of virtualization technology.