Taking into account the merits of anticipatory reflection, instructional planning is perceived as an important process in the professionalization of teachers. When implementing a complex instructional strategy such as collaborative learning (CL), a thorough preparation becomes even more important. The purpose of the present study was to investigate the quality of lesson plans focusing on CL implementation. Based on the literature, a scoring rubric with 17 criteria in three domains (instruction, organization and evaluation) was developed and applied to analyse 323 lesson plans of second-year pre-service teachers. The results reveal both strengths (e.g. designing appropriate learning tasks, developing adequate learning materials) and weaknesses (e.g. including social objectives, rules and agreements for collaborative work) in the lesson plans. The rubric proves to be a useful instrument both for research and practice-oriented reflection. The findings provide significant insights for teacher training with regard to CL implementation. (Contains 3 tables.)