This qualitative study of L2 writing processes aims to make a contribution to the field of propaedeutic writing in general and to material-based composition in particular. Its specific focus is on criteria-based comparisons within texts collaboratively written by Hungarian students in German as a foreign language in school year 11. Two texts composed by groups of three writers each and the respective transcripts of their collaborative interaction are analyzed with respect to the learners’ attempts at structuring and synthesizing the reading materials provided with the writing task as well as with respect to the challenges they struggle with. The analysis shows that the students do not plan their collaborative writing at a macro level and that they arrive at texts in different comparison formats and levels of synthesis. This explorative study thus generates hypotheses for further investigation of writing from sources in teaching German as a foreign language at school level as well as the development of a progressive propaedeutic writing program across the curriculum.