Almost all of the countries in the world are developing their online-government, or e-government (EG), systems with the support of information and communication technology (ICT). Countries are gradually enhancing their service scope, functionality, and flexibility to meet strategic goals set at the policy stage and to satisfy user requirements. For investment justification, necessary modifications, further development, and future guidelines assessing the performances of those EG projects are imperative for any country. This chapter is designed to develop a comprehensive model (E-government Performance Matrix - GPM) from the practitioner's perspective to measure the performance of ongoing EG projects. This chapter has four sections with sub-sections.