The practice of reasoning has been regarded as core element for developing mathematical arguments. However, curricula reforms have only recently focused on reasoning as an essen- tial part of mathematics education. In Sweden, the emphasis on systematically developing reasoning competences began in 1994 and became even more explicitly focused in the 2011 mathematics curricula reform documents. However, many stu- dies, including our own, show that students and teachers face difficulties in conceiving what reasoning might mean and also how its growth can be supported in the everyday mathematics classroom setting. Through a collaborative intervention study, the present paper explores how the coordination amongst the basic tenets of Reciprocal Teaching and Systemic Functional Lin- guistics perspectives could potentially create a pedagogic design for Grade 4 students’ reasoning in specific mathematical tasks.