In this study we applied a discursive perspective of learning (Sfard, 2008) to a sequence of 21 geometry mini-lessons taught in a fourth grade classroom. From this perspective, learning is defined as changes in mathematical discourse. We first characterize and then compare discourse from the beginning and the end of the mini-lesson sequence. We identify shifts in the discourse that occurred during the sequence. We then discuss how the characteristics of the students' geometric discourse informed task design and instruction. This perspective provided a useful means for linking instruction to student learning in an operationalized manner. [For the complete proceedings, see ED606556.]