The Middle Grades Mathematics Project (MGMP) has been an effort to produce exemplary mathematics curriculum units for grades six, seven, and eight, evaluate the compatibility of those units in classrooms, and to study the nature of the effort needed to help teachers to teach the units effectively in their classrooms. Each activity designed by MGMP is intended to be taught using an instructional model based on three phases: launching, exploring and summarizing. Teaching the MGMP materials places demands on the teacher relative to both the content and to the instructional model. This study examines the impact of coaching as a strategy in changing teachers' instructional emphasis on producing the desired instructional changes. Changes in teachers' beliefs and behaviors included patterns of communication, teaching, planning for instruction and instructional thoughts and actions. Discussions include: (1) research questions; (2) theoretical framework; (3) methodology including development of instrument, observations, summer workshop, materials production and coaches; (4) the intervention; (5) results and discussions; and (6) conclusions and implications. Appendices include the study instruments and three case studies of teachers involved in the project: (1) a study of a lead coached teacher; (2) a study of a coached teacher; and (3) a study of an uncoached teacher. The study concludes that summer workshops were effective in assisting teachers with the MGMP units and that coaching is an effective strategy in promoting teacher change. (CW)