This study investigated preservice teachers' (PTs) conceptions of how math is well-taught, their ability to design lessons that employ reform-based practices, and relations between their conceptions and lesson plans. We developed a survey and a rubric, in relation to the most recent standards and practices in U.S for the teaching and learning of math, to measure conceptions of how math is well-taught, and to measure the quality of a lesson plan. We designed and implemented a series of activities based on most recent reform-based standards and practices in a math methods course. The results showed significant change in PTs' (n = 68) conceptions, however, there was not any significant relationship between their conceptions and their capability of designing reform-based lesson plans. While significant change occurred both in PTs' conceptions and lesson-planning styles, the scores indicated that they were not yet fully convinced, nor fully capable. Suggestions and implications for teacher educators are discussed.