Employees often come together in coalitions to voice concerns and suggestions. However, such coalitions have achieved limited success thus far in advocating gender equity issues within organizations. I argue that the homophily that women demonstrate when forming coalitions on gender equity can explain their lack of effectiveness. I theorize that successful coalitions, via their composition, signal to endorsers that the issue they are advocating is organizationally relevant. Although female-only, compared to male-only, coalitions are seen as having the legitimacy to speak up about gender equity, they struggle to convince stakeholders that the issue is broadly relevant. I posit that mixed-gender coalitions, via the joint participation of women and men, can both signal sufficient legitimacy to voice about a gender equity issue while also conveying that the issue is not niche and holds relevance for everyone in the organization. As a consequence, such gender-diverse coalitions are uniquely positioned to earn higher support for gender equity issues relative to alternative, gender-heterogeneous configurations. In Study 1, a quasi-field experiment, 714 participants responded to their coworkers putatively advocating a gender equity issue in the workplace. Mixed-gender coalitions outperformed both female-only and male-only coalitions on issue support, as explained by advantages in both perceived legitimacy to speak up and perceived organizational relevance. The same pattern was found in Study 2, a fully randomized experiment involving 891 United States-based workers participating in an immersive managerial simulation. With this dissertation, I demonstrate that coalition diversity holds signaling value to potential endorsers, irrespective of any internal, functional value such diversity may bring to the coalition itself through a pooling of skills and resources. I additionally highlight that advocating for gender equity is a political process and women should enlist men as allies to better sell the issue within organizations.