Learning how to plan a lesson is central to teacher education, yet there is only little research so far that has investigated how well student teachers write lesson plans. The aim of this paper, therefore, was to explore the competence of student teachers in lesson planning, with a special focus on the Cameroonian context. More specifically, the study sought to find out which stages and aspects of lesson planning caused more difficulty to trainee teachers, and whether collaboration led to better lesson plans. Data consisted of 101 lesson plans, among which 74 were planned by single trainee teachers and 27 planned by groups of two or three teacher candidates. These lessons were collected across two years through a graduate-level English language teaching methodology course. The findings reveal that trainee teachers had more difficulty writing lesson outcomes, aligning lesson outcomes with assessment, providing variety in assessment and quality take-home assignment as well, and asking relevant questions to guide student work. Also, it was found that joint lesson plans contained fewer errors and were better in terms of instructional quality than lessons planned by single teachers. Teacher education programs, therefore, should adopt microteaching and joint lesson planning activities for their potential to improve student teachers' competence in lesson design.