This study focuses on teacher professional learning in early childhood education and care (ECEC) in response to the contemporary challenge of understanding the role of teachers in play. It explores the learning process of teachers when investigating how an ECEC work team in Sweden collaboratively changes their way of reasoning regarding their role in play when introduced to a theoretical framework that takes on this topic. This study is part of a combined research and development project, including focus group conversations (FGC) with video-stimulated recall. From a sociocultural perspective, the findings show how the participants' reasoning is mediated and re-mediated at two levels. The first level includes the re-mediation of the concept of steering (from a more negative connotation to a more positive one). The second level explores how this shift re-mediates the team's reasoning regarding their role in children's play, from uncertainties regarding the risk of over steering the play to reasoning about the teacher's key role in play for teaching to take place. Another finding focuses on the nonlinear progression of learning, as reasoning evident in the first FGC remained in the last but to a lesser extent. Implications for professional development training are discussed.