Openness to homosexuality at the congregational level of American religious life has only recently received scholarly attention. This research reports patterns of membership openness to gays and lesbians among American Christian congregations and synthesizes emerging hypotheses to explain such openness. Using data from the second wave of the National Congregations Study (Chaves 2007), multinomial logistic regression models demonstrate evidence for the importance of clergy characteristics, membership demographics, local context, local theological culture, and religious tradition. A boundary-bridging cultural model also conceptualizes how the bridging practices of congregations influence membership openness. Interfaith volunteering and interracial worship express an organizational approach to social boundaries that prioritizes diversity and openness. With a controversial social issue (homosexuality), and a relative lack of local organizational processes to deal with such an issue, boundary-bridging customs may shape the sexuality boundaries of congregations. This research develops knowledge of cultural processes and homosexuality within American religious congregations.