Ideological positions regarding social diversity and status inequality are examined as predictors of people's willingness to engage in collective action. Using social dominance theory and social identity theory, we hypothesized that the relationships between ideology, ethnic identification, and orientation toward collective action will vary depending on the position of one's group. Comparisons were made between four U.S. groups: White natives, White immigrants, Black/Latino natives, and Black/Latino immigrants. Groups differed in their endorsement of social diversity and social inequality, as well as in their orientation toward collective action and their ethnic group identification. For all groups, ethnic identity mediated the link between ideology and collective action, but the valence and magnitude of paths differed as a function of ethnicity and immigrant status. Social diversity was more critical for U.S. immigrants (White and Black/Latino); social inequality accounted for more variance in native-born U.S. groups (although in opposite directions for the two groups).