This chapter summarises the work undertaken in the Engineering Strand of the OECD's Assessment of Higher Education Learning Outcomes (AHELO) Feasibility Study. The iterative processes of design, review and revision that were followed to ensure that the assessment instrument and scoring processes were of high quality are outlined in detail. There are several lessons which can be drawn out of these experiences for future practice. The chapter offers an example of the amount of thinking and effort that is required in the development of an assessment instrument and the scoring processes related to it, if high quality data and directions for educational improvement are the desired outcome.