Though it is well known that pre-service teachers' field experiences are recognized as key to enhancing teaching practice, Taiwanese pre-service teachers who take "Teaching Methods and Materials" in elementary school's seven areas often complain that they lack field experience. They do not have the opportunity to experience teaching demonstrations among real elementary school students. This case study discusses 35 pre-service English teachers' professional learning and the field experience they acquired from expert teachers in the Teaching Methods and Materials of English in the Elementary School course in Taiwan. Data in this study include: (1) observation notes, (2) lesson plans, worksheets, and teaching materials, (3) videos on teaching demonstrations, (4) conversation notes on lesson planning, (5) the class syllabus, (6) semi-structured interviews with expert teachers, and (7) participants' reflections on their mentoring experience. Participants held positive attitudes toward the mentoring experience and their expert teachers. Because it helped them combine their knowledge of the classroom context, lesson plan content, instructional pedagogy, and their students, these 35 participants regarded teaching practice as more beneficial than observing expert teachers' instructions and having conversation with expert teachers after teaching practice. In addition to mentored field experience, online discussions and seminars on topics are suggested for inclusion in mentoring activities.