Preservice teachers often have knowledge of the latest and best educational practice and need opportunities to apply theory in a "real world" setting through optimal field placements. A review of the literature on the relationship of the preservice teacher and the cooperating teacher revealed that while serving as a cooperating teacher provided its own tensions, it also was an important professional development opportunity for the cooperating teacher. The document focuses on a highly successful 8-week preservice placement involving Mary, the cooperating teacher with more than 25 years of experience; Ann, the preservice teacher; and the university supervisor. The study also looks at the use of "whole language" method of teaching reading. Mary had little background in whole language, while Ann brought a substantial theoretical background in the method. The placement gave Ann the opportunity to apply the whole language method in a real-life situation and to get feedback and support from an experienced teacher in a collegial setting. Ann reported that though she was initially nervous about being the information provider, Mary's encouragement and eagerness to learn gave her the confidence to experiment with the whole language approach. Mary was enthusiastic about learning a new way of teaching and stressed the importance of watching Ann model the teaching; she appreciated the benefit of collaboration in developing ideas. Findings suggested that the more familiar supervisors are with what preservice teachers have learned in their classes, the better they can help and support both cooperating teachers and preservice teachers. (Contains 16 references.) (ND)