This study offers timely empirical evidence of the magnitude of the language effect on the performance of different language user groups, namely English as a Foreign Language (EFL), English as a Second Language (ESL), and English as a Native Language (ENL) in an accounting program instructed in English, an area that has been under researched. Informed by Cognitive Load Theory (CLT), this study develops an innovative research methodology (crossover repeated measures design), drawing on a large data analysis (n=2912) of students' academic results in six accounting specialisation subjects between 2007 and 2014 in an Australian university's undergraduate accounting program. Results show that while all language user groups perform worse in more conceptually (MC) oriented subjects compared to less conceptually (LC) oriented subjects, the relative performance between MC and LC is strongly related to English language user groups. For the first time the magnitude of the impact is derived. The study has implications for the instructional design of accounting programs in English-speaking universities and their offshore programs in non-English speaking countries.