Phonological awareness (PA) is at the foundation of reading development: PA is introduced before formal reading instruction, has predictive value for later reading abilities, is a primary target for early intervention, and is considered one of the core mechanisms in developmental dyslexia. Conventional approaches to assessing PA are time-consuming and resource intensive: assessments must be individually administered, require expertise, and scoring verbal responses is challenging and subjective. Therefore, we introduce a rapid, automated, online measure of PA — The Rapid Online Assessment of Reading - Phonological Awareness (ROAR-PA) — that can be widely implemented in classrooms and research studies without a test administrator. We explored whether this gamified, online task, that relies on touchscreen/click responses, can serve as an accurate and reliable measure of PA and as a good predictor of reading development. We found that ROAR-PA is well correlated with standardized measures of PA (CTOPP-2, r = .80) and reading (Woodcock-Johnson, r = .50), for children from Pre-K through fourth grade and achieves exceptional reliability (𝜶 = .96) in a 12-minute automated, online assessment. Furthermore, validation in 50 first and second grade classrooms shows reliable implementation in large, public school classrooms with predictive value of future reading development.