This study explored how a collaborative approach in teaching for disciplinary academic writing would influence the transfer of learning in postgraduate students with varied writing proficiency levels. A sample population of 58 medical students majoring in four different medical sciences participated in this research. Throughout a whole semester, discipline-specific writing skills that were collaboratively planned were instructed. Meanwhile, the researchers recorded the trace of variance in students' writing practices and finally correlated the variance with the students' initial proficiency scores. To benefit the merits of qualitative analysis and to obtain specific information about the values and opinions of the population, the researchers also conducted focus group interviews after each training session. Results indicate that owing to the collaborative design of the program, the participants could attain significant levels of writing skills and finally transfer their received instruction to authentic practices. Further analyses of the results imply that age, university admission criteria, and level of professional involvement could have a determining interplay with students' varied writing proficiency levels.