This study examined the longitudinal prediction of decoding, oral reading fluency (ORF), and bilingual language proficiency (BLP) on student reading comprehension (RC) outcomes in Spanish and in English. Participants were first-grade Latinx students attending bilingual programs. Findings indicated that BLP initial status and gains were significant predictors of Spanish and English RC at the end of second grade. English and Spanish decoding in first grade, in addition to BLP, explained 27 percent of the variance in English reading comprehension. However, only Spanish decoding was a significant predictor of Spanish reading comprehension. Once English and Spanish second grade ORF scores were added to the model, decoding no longer explained any of the variance in RC. BLP, English ORF initial status and gains, and Spanish gains explained 47 percent of the variance in English reading comprehension. BLP and Spanish ORF initial status explained 46 percent of the variance in Spanish RC. [For the corresponding grantee submission, see ED618408.]