This study investigates the processing behaviors of a group of Brazilian bilingual students, instructed, advanced English students (n equal 21), and an English monolingual control group (n equal 11) during their comprehension of Present Perfect and Simple Past sentences in an on-line, self-paced reading (SPR) task. An off-line Acceptability Judgment Task (AJT) provides a baseline measure of explicit knowledge in order to validate the on-line results. The results are compared, qualitatively, between the bilingual and monolingual groups in order to investigate their sensitivity to experimental manipulations in Tense/Aspect, adverbial (Mis)match, and Telicity. The Present Perfect was used for the stimuli as it is a late-acquired feature of English which allows for the study of processing strategy of advanced level students. While both groups were able to recognize Mismatches off-line, monolinguals were not sensitive to the Mismatch condition in the on-line experiment. Surprisingly, the bilingual group showed more sensitivity to the adverbial Match variable, showing a processing facilitation in the Match condition as well as some mismatch sensitivity as well. The monolingual group showed significant effects for Telicity at multiple sentence regions. Some qualitative differences were seen between the two groups in their reading-time contours across the verb phrase. The monolinguals show within-group consistency across multiple conditions and signs of integrative processing (wrap-up) effects in their processing patterns which are not seen among the bilingual group. There are currently no studies with similar experimental conditions which investigate the on-line comprehension of the English Present Perfect with Brazilian Portuguese-English bilinguals in comparison to American English monolinguals.