Spanish and Catalan speakers often face difficulties when learning the English vowel system. Acquisition of English schwa (/ə/) is of particular interest, because Majorcan Catalan has a stressed /ə/ in its phonemic inventory. PAM/PAM-L2 posits that native language experience shapes perception of L2 sounds, so discrimination of L2 contrasts can be predicted from L2-to-L1 categorization. The current study focused on whether discrimination of the vowel contrasts /ɛ/-/ə/, /ʌ/-/ǝ/, and /ʊ/-/ǝ/ can be accounted for by the perceptual assimilation of these vowels onto L1-Catalan categories. Spanish-Catalan experienced learners of English performed a categorization with goodness rating task and an AXB discrimination task. The four vowels of interest, /ɛ/, /ʌ/, /ʊ/ and /ǝ/, were perceived as uncategorized and the contrasts involving /ǝ/ differed in the degree of perceptual overlap. Specifically, /ʊ/-/ǝ/ was non-overlapping, /ɛ/-/ə/ was partially overlapping, and /ʌ/-/ǝ/ was completely overlapping. Discrimination was poorer for /ʌ/-/ǝ/ than the other two contrasts. However, contrary to PAM predictions, no differences were found between the partially overlapping contrast /ɛ/-/ə/ and the non-overlapping contrast /ʊ/-/ǝ/. Overlap scores for individual participants were not related to discrimination accuracy, suggesting that predictions of L2 discrimination based on L2-to-L1 categorization should be made at the group level.