Content language integrated learning (CLIL) instruction has become a popular practice in Taiwan. Teachers should be aware of the nature of tasks and outputs to identify to what extent tasks can be designed for learners to engage in the expression and understanding of the academic content. This case study analyzed 38 Taiwanese elementary school English teachers’ design and implementation of pushed output as tasks for six CLIL lessons in four content areas of life, arts, alternative curriculum, and integrative activities. The thematic analysis of interviews, observation fieldnotes, lesson plans, and worksheets led to the following major findings. First, teachers’ misconceptions on and lack of competence of CLIL, and external professional support on curriculum development affected the teachers’ designs on pushed output. Second, teachers’ negligence of instruction on the language for learning and insufficient provisions of sentence patterns on the language of learning led to their learners’ limited output on the target language and the use of the mother tongue during pushed output. Suggestions for the effective design and implementation of pushed output for CLIL were provided in terms of equipping teachers with competence on CLIL, collaboration between content and language teachers, and reflective practice on CLIL instructional strategies.