Vowel systems are a rich source of information about speakers’ social affiliations and linguistic influences. With the purpose of contributing to recent dialect investigations of immigrant communities inside the US, this study examined the acoustics of bilingual Persian-Oklahomans and their participation in Oklahoma dialect features. Twenty Oklahoma-born second-generation Persian-Americans were compared to ten monolingual European-Oklahomans with respect to their production of local dialect features. Results showed similar vowel spaces between the groups indicating that second-generation Persian-Oklahomans participated in the local mix of Southern and Midland features, with one notable exception: they did not display the pin/pen merger, a feature of Southern dialects. Similar studies on European-Oklahoman speakers suggested a uniform presence of pin/pen merger among Research on the Dialects of English in Oklahoma (RODEO) project respondents. However, Persian-Oklahomans’ productions of these vowels were consistently unmerged across the continuum of speech styles. Accordingly, this study argues for a connection between this acoustic variation and speakers’ demographic traits, make-up of social network, and heritage Farsi despite their frequent contact with the merger and their rich social network with middle-class European-Oklahoman speakers of the Oklahoma dialect.