Teacher assessment literacy (AL) is a concern for both educational assessment and teacher education research. As part of teacher AL, teacher competency of assessment planning has remained underexplored. To address this gap, this study explored how a group of 20 contest-winning university English teachers in China planned for assessment through qualitative analyses of their lesson plans and follow-up teacher interviews. The findings show that: (1) lesson plans include assessment-related components such as teaching objectives, student background, instruction-embedded assessment, and after-class assessment tasks; (2) their assessment planning is characterized by a clear understanding of learning goals, but an absence of rubrics and exemplars for performance assessments, over-reliance on groups as target of assessment, and inconsistencies between learning objectives and assessment tasks; and (3) their assessment planning was mainly intuitive and instruction-oriented. This paper concludes with a working model of assessment planning, and discusses a future research agenda for assessment planning.