<p>Current reading research remains Latin script-centric in a monoliterate context, and may not be generalizable to the significant percentage of school-aged children growing up as biscriptal bilinguals globally. To address this, we examined the early stages of reading development in bilingual readers of an under-studied language combination that differs across orthographic depth and script. Our longitudinal study compared within-language contributions of three phonological processing skills to reading outcomes in Urdu-English bilingual children. We assessed 154 Urdu-English readers in Pakistan and Canada on phonological awareness, phonological memory, and rapid automatized naming (RAN) skills at Timepoint 1 (Senior Kindergarten) and word/non-word reading accuracy and fluency outcomes at Timepoint 2 (Grade 1) in Urdu (orthographically-transparent language with Perso-Arabic script) and English (orthographically-opaque with Latin script). Our multivariate multiple linear regression analyses demonstrate the importance of phonological awareness and RAN for reading, across orthographic depth/script and type of reading outcome measure. Predictive strength differences were also evident. Phonological awareness accounted for greater variance in reading accuracy across both languages and particularly in Urdu, with RAN contributing greater variance to Urdu reading fluency. Phonological memory was not a significant predictor in either language. Our study supports the generalizability of dominant reading models, such as Psycholinguistic Grain Size Theory (PGST), Orthographic Depth Hypothesis (ODH), and Speed-of-Processing theoretical account of RAN-reading fluency relationship, beyond monoliterate readers of Latin scripts. Particularly, we demonstrate the importance of phonological awareness and RAN for reading outcomes in biliterate readers of a transparent orthography with a Perso-Arabic script.</p>