This study draws on theories of collective action and organizational ecology to investigate a particular type of voluntary association: mixed-mode groups. Mixed-mode groups are created and organized online to meet physically in geographically defined ways. An online survey was conducted with 171 randomly sampled groups on Meetup.com—a website that facilitates the creation and coordination of mixed-mode groups. Analysis shows that even when a mixed-mode group implements strategies focused on internal group processes, it benefits from tapping into its external networks to obtain resources for group operation. Also, the differential impacts of internal and external strategies indicate that in the case of environment-prone mixed-mode groups, implementation of internal strategies alone, with or without solicited external networking resources, is helpful for generating positive group outcomes. Together, these results establish that boundary spanning represents not only a type of strategic action to obtain resources and produce positive outcomes but also an inherent and defining mechanism of contemporary voluntary groups for engaging in collective action.