Against the background of providing learning opportunities for meaningful mathematics for all students, the presented Design Research study had the goal of investigating how to support students facing language barriers while learning mathematics in phases of unmoderated group work. For this purpose, learning meaningful mathematics and demanding discourse practices are connected with quality interaction characteristics identified in research on productive group work. This theoretical consideration was implemented in a learning arrangement on similarity by means of four design principles for enhancing language in group work on meaningful mathematics. The empirical insights show to what extent the intended demanding discourse practices and quality interaction characteristics can be identified in different steps of knowledge construction, and to what extent they are supported by the design element 'role cards'. Instead of calling for less unmoderated group work for students facing language barriers, the results of the study suggest that more research is needed to design scaffolds matching students' needs, aside from whole-class discussions.