In the last two decades, online computer-marked assignments (CMAs) have been widely used in accounting education. Although there is a growing body of research on this form of online assessment, most of the previous studies relied on small samples of respondents or focused on student self-report using survey methods. This exploratory mixed-method study aims to combine a quantitative analysis of learners' academic performance on an online Financial Accounting course with a more in-depth exploration of learner experiences using qualitative methods. The quantitative findings suggest that student previous educational qualifications, age and experience of studying a similar subject are strongly associated with CMA completion, which is also linked to scores on other pieces of assessed work. The qualitative results show that from the learners' perspective, diversifying assessment methods, introducing low-stakes assessment activities and creating opportunities for situational interest are viewed as key aspects of online CMA design. This paper concludes with discussing the implications of the study for designing and delivering online courses in accounting, particularly in the light of the growing popularity of massive open online courses (MOOCs). [For the complete volume, "Advances in Accounting Education: Teaching and Curriculum Innovations. Volume 24," see ED661366.]