This study examines master's and doctoral theses on English preparatory classes at tertiary level in Turkey in terms of completion year, thesis type, subject areas, data types, research design, sample groups, problem statements and recommendations. This study is a systematic review of literature and the data was collected through document analysis technique. Content analysis was carried out on the theses selected through criterion sampling method. A total of 82 theses, which were completed by July 2017, were included in the analysis based on inclusion criteria. The analysis reveals significant results as to theses on English preparatory classes at universities. The most frequent subject areas in the theses were identified as learning styles/strategies, motivation/attitude/belief, program evaluation, increasing vocabulary knowledge, reading skills and foreign language anxiety respectively. The majority of the theses rest on quantitative data and employ descriptive research designs. Samples in the theses mostly consist of students while few of them address instructors. The most frequent themes in problem statements include inadequacy, importance and failure while the most frequent recommendations are about motivation and anxiety, and in-service training. This study has the potential to guide future research by putting forth research trends in graduate research on English preparatory classes at tertiary level.