This study investigated the development of the English vowel contrasts /i-ɪ/, /u-ʊ/, /ɛae/, and /ɑ-ʌ/ produced by Ecuadorian Spanish speakers enrolled in the First and Second Language Teaching program at a State University in Ecuador. Recorded at six-month intervals at the end of the third, fourth, and fifth semesters, they produced 40 isolated English monosyllabic words. Each block of vowel contrasts had familiar words representing five words per vowel in a CVC and CVCC context. To examine pronunciation differences in the acoustic vowel space development over time, the Euclidean distance between the four groups of vowel contrasts was calculated based on F1 and F2 frequency values, which were Lobanovnormalised and analysed using a mixed-effects model. The results showed that Ecuadorian learners' pronunciation did not vary in the general learning trajectories over the three recordings, and did not match the native English criteria by the end of the study. However, Ecuadorian learners showed high variability within subjects and between subjects in the production of each vowel contrast over time. In summary, these results suggest that withingroup, not all Ecuadorian learners followed the same developmental trajectories and varied depending on the vowel contrast.