Couched in Harmonic Serialism, this paper uses as examples echo vowel epenthesis in four Austronesian languages—Budai Rukai, Maga Rukai, Selayarese, and Rarotongan—to demonstrate that epenthesis, like many other phonological phenomena, involves gradual, harmonically improving derivations. This paper also draws a comparison with parallel Optimality Theory to show that Harmonic Serialism is a more satisfactory theory of vowel epenthesis in terms of typological prediction.