We demonstrate that Fauconnier and Turner's theory of conceptual blending, originally a theory of the mind that focuses on the individual, can be used as a tool for analysis of group discourse processes. Building on sociocultural theories that consider cognition a social process, we propose blending theory as a descriptive and analytic tool for use in examining the processes of collective reasoning. We present data from focus groups at University of Colorado Boulder in which Modern Physics students engage in reasoning about quantum phenomena and negotiate ontological conceptions of quantum entities such as electrons and photons (i.e. negotiating what kind of a thing an electron or photon is). We present a conceptual blending analysis of group discourse within this context, and show how conceptual blending theory can be used to describe both collectively constructed blends and more traditional individual blends.