The lack of preparation for cooperating teachers is a long-standing problem in teacher education, as is the haphazard nature and quality of field experiences. This study of 119 preservice and 146 cooperating teachers in 10 university-based credentialing programs in California examined the difference preparation made in how cooperating teachers enacted their role, as well as the relationship between preservice teachers' perceptions of cooperating teacher practice and their ratings of their field experience. A significant finding was that cooperating teachers who received preparation for their role reported greater enactment of practices overall and in particular practices related to prompting reflection and goal setting. Preservice teachers' field ratings strongly correlated to their perceptions of cooperating teacher practice. Implications are for design and implementation of professional development for cooperating teachers to improve field experience quality.