The English for Specific Purposes (ESP) field is currently receiving a lot of attention as researchers and practitioners seek to improve the learning experience for the students and raise the quality of the courses. To advance ESP practice, it is crucial that teacher training in ESP is enhanced and supported through exemplary practices. Vocabulary development is established as a central trait in ESP, yet it still poses a challenging aspect of the teaching practice. This chapter discusses a specific vocabulary task through which guidance is provided to teachers in order to facilitate the development of ESP vocabulary in their ESP teaching contexts. This research reports on the results of data collected from a course in a tertiary institution in Cyprus where ESP students worked collaboratively to create an online biomedical dictionary on a wiki. The research conducted is qualitative, and grounded theory was applied. Finally, this chapter concludes with certain criteria which afford the application of this vocabulary enhancement task in any ESP and English as a Foreign Language (EFL) course across different language levels as well as in mixed ability classrooms. [For the complete volume, "ESP Teaching and Teacher Education: Current Theories and Practices," see ED595614.]