Despite the increasing use of virtual modalities in schools since the COVID-19 pandemic, no systematic tools exist to evaluate the process of online learning. We developed and validated an Online Learning Process Questionnaire (OLPQ) for assessing online at-home learning among 219 Hong Kong primary-school students and 474 caregivers. Exploratory and confirmatory factor analyses of caregivers' data classified the 58-item OLPQ into 11 subscales: (1) learning aims, (2) environmental structuring, (3) learning environment, (4) time management, (5) engagement in learning activities, (6) persistence, (7) interaction between teachers and students, (8) interaction among students, (9) feedback from the interface, (10) application of learning, and (11) meaning of learning under three learning phases. Confirmatory factor analysis of students' data further categorized the 11-subscale framework into three learning phases: preparatory, performance, and transfer. The OLPQ demonstrated excellent reliability and discriminant validity across caregiver (Cronbach's alpha = 0.98) and student samples (alpha = 0.98). These findings indicate that the OLPQ is a valid and reliable instrument for assessing the online at-home learning process among both students and their caregivers.