In this paper, the spectral properties of vowels in three Australian languages are examined with the aim of determining whether prosodic prominence and domain-edge effects on formant frequencies, formant variability and vowel space dispersion can be identified. It is shown that these vowel systems are sufficiently dispersed, with an anchoring of the system by the open central vowel. It is also shown that for Burarra but not for Gupapuyngu or Warlpiri there is some evidence of prosodically-driven hyper-articulation. Finally, the data indicate pre-boundary lengthening in all three languages, which in some cases appears to be associated with changes in vowel quality.