The current study examined self-reported first language (Spanish) language reading and writing ability and behavior and relationships with digit span and stroop task performance. A battery of assessments and questionnaires was administered to 81 sequential Spanish-English bilingual university students in the U.S., for whom the sole language of education is English. Hierarchical regression models revealed self-reported amount of Spanish used for academic writing uniquely accounted for 17% of variance in digit span forward scores, controlling for non-verbal IQ. Self-reported Spanish reading and writing ability also significantly predicted higher digit span forward scores and stroop task performance. Findings indicate that vectors of within-population difference related to L1 academic reading and writing are associated with differences in verbal short term memory and inhibition. Findings underscore the importance of considering diversity within bilingual samples and further support theories of a continuum of bilingual experience intensity, which is related to outcomes.