In this study, we draw upon a social movement perspective to examine how movements and institutional opportunity (political and cultural) influenced a sample of Fortune 500 corporations’ adoption of a controversial organizational practice—same-sex partner health benefits. Our results show that while corporations’ gay, lesbian, bisexual, and transgender (GLBT) employee resource groups increased the rate of the corporations’ benefits adoption, the effect of the GLBT employee resource groups became weaker when the degree of resource concentration of local GLBT advocacy organizations was high. Political opportunity derived from state legal environments and cultural opportunity derived from the tenor of moral legitimacy in leading national press coverage had little influence on the rate of benefits adoption. Furthermore, the influence of a GLBT employee resource group on the rate of benefits adoption by its corporation became weaker when cultural opportunity, derived from increases in positive tenor of pragmatic legitimacy discourse used by movement and countermovement organizations in the press, was present. Accordingly, our study shows the complicated effects of movements within and outside corporations and cultural opportunity on the adoption of a controversial practice and reveals the importance of mobilizing structure (both internal and external movements) and cultural opportunity in the adoption.