The aim of this paper is to analyze mid vowel segments as pronounced by a group of adolescents who speak Spanish and the Catalan variety of Lleida and whose L1 is Catalan or Roumanian. The analysis is based on a linguistic component related to the phonological contrast of both languages, Catalan and Roumanian, as well as to social and sociolinguistic variables such as gender, the length of time of residence in the welcoming country, and language usage and assessment of the participants in the pronunciation poll. The results show differences in the production between mid vowels [ɛ] and [ɔ] related to: 1) the degree of openness (F1) of the two segments, since vowels articulated by L1 Catalan speakers are the lowest; 2) the distance between the F1 of [e ɛ] and [o ɔ], which is greater in those articulated by L1 Catalan speakers; 3) the length of the vowels, for they are usually shorter in the speech of L1 Catalan speakers. The most statistically significant variables were as follows: gender (Catalan girls present higher F1); the usage frequency of Catalan by L1 Roumanian speakers (those with the highest usage frequency articulate [ɛ] and [ɔ] with a higher L1, i.e. their vowels are more open); and the high levels of Catalan usage, which may also have an influence on production.