This formative evaluation study of a professional development institute for K-12 educators examined immediate outcomes and short-term impacts on participants' learning and change in mathematics teaching practice. Participants' journals and interviews were analyzed using qualitative methods and a grounded theory (the discovery of theory from data—systematically obtained and analyzed (see 1967 book of Glaser and Strauss)) approach. Findings highlight the fact that while participants had previous knowledge and understanding of an inquiry approach to mathematics instruction, this knowledge was refined and reinforced through course participation. Some, however, continued to evidence a more limited or narrow conception of inquiry. Many applied aspects of an inquiry approach following the institute—small, but fundamental changes in classroom practice considered ‘seeds of change’.