The literature on collective action in support of equality without regard to sexual orientation or gender identity has emphasized the role of lesbian, gay, bisexual, and transgender (LGBT) activists. Relatively little attention has been given to the role of members of the advantaged group, heterosexual allies who work for equality. This study presents data from an ongoing study of 127 allies who have been visibly active in these efforts in the United States. The findings suggest two major sets of ally motives: those rooted in fundamental principles (justice, civil rights, patriotism, religious beliefs, moral principles, and using privilege to positive ends) and those based on personal experiences or roles (professional roles, family relationships, valuing marriage, achieving closure on personal experiences, transforming guilt, and anger). The findings suggest that the concept of opinion-based groups holds promise for conceptualizing and mobilizing LGBT–ally collective action.