The notion of opportunity, as currently discussed in entrepreneurship research, is theoretically exciting but empirically elusive. This article seeks to stimulate a new conversation about entrepreneurial opportunities by distinguishing two conceptions of entrepreneurial behavior—formal and substantive—and situating the construct of opportunity within the latter. It discusses three substantive premises for studying opportunities empirically: (1) opportunity as happening; (2) opportunity as expressed in actions; and (3) opportunity as instituted in market structures. These premises stimulate research questions that can invigorate and expand the study of entrepreneurial opportunities. They invite a continuous dialogue between qualitative and quantitative methodologies in behalf of understanding how opportunities emerge and evolve at the level of individual entrepreneurs.