In some languages, epenthetic vowels act as though they are invisible to stress assignment. There are many proposals for addressing this problem in various languages; however, the challenge is particularly acute in Classic OT because the markedness constraints responsible for stress only evaluate surface forms. This paper presents a new proposal within the framework of Harmonic Serialism, a version of OT that combines constraint interaction with serial derivation. This proposal accounts for opaque stress-epenthesis interactions using only traditional constraint ranking, with no machinery beyond the adoption of a serial, rather than parallel, framework. This paper shows that Harmonic Serialism retains many of the advantages of Classic OT, including factorial typology by constraint permutation and the use of constraint ranking to account for non-uniform interactions, as evidenced from analyses of stress-epenthesis interactions in Egyptian Arabic, Dakota, and Levantine Arabic.