In tertiary education settings it is imperative for students to move confidently between the academic discourses of a variety of disciplines. Thus, it is merited to aim writing interventions at genres that straddle disciplinary boundaries. Following a survey on preferred genres and text types at the University of Pretoria an essay-writing intervention for second-year undergraduate students was designed and developed. The effectiveness of the intervention was evaluated using a pretest-posttest design. On
average the scores of the respondents improved by 7%. The largest improvement was on structure and development (15%), followed by the use of source materials (10%) and academic writing style (7%). An interpretation of the findings, combined with feedback from the respondents, suggested that extensive writing should be introduced soon after the commencement of an essay-writing intervention, and that a series of shorter teaching and learning cycles might be more effective than a single cycle. Furthermore, study units dealing with making and supporting claims might focus more strongly on learning from models than on explicit teaching of a variety of disciplinary conventions and preferences.