This article carries out a cross-European comparison of stakeholder perspectives on catering to diversity within CLIL programs. It reports on a cross-sectional concurrent triangulation mixed methods study with 2,526 teachers, students, and parents in 59 Secondary schools in six European countries: Austria, Finland, Germany, Italy, Spain, and the UK. It employs data, methodological, and location triangulation and carries out across-cohort comparisons in order to determine the differences/similarities which can be discerned between the measures implemented in northern, central, and southern Europe to make bilingual education a more inclusive reality for all. It also provides comparative insights into the main difficulties and chief training needs which still need to be addressed. The broader take-away is that CLIL provision, as it stands, does not fit the bill in the new mainstreaming scenario and needs to be reengineered to respond to the needs posed by educational differentiation. This pan-European outlook will allow us to determine where we currently stand on this issue and to showcase the main lessons which can be gleaned from different contexts in order to step up to one of the most important challenges facing bilingual education in Europe (and beyond) if we seek to ensure its sustainability.