The study aims to provide a current synthesis of assessment methods in Online Inquiry-Based Learning (OIBL) systems that use argumentation as a pedagogy. Three databases were used, namely, Scopus, Web of Science, and ERIC, for data collection. The present review analyzed 73 studies from 2010 to 2023. A qualitative content analysis examined the assessment methods used in inquiry-based systems. Results showed that most studies used direct methods of assessment followed by indirect methods. Among the direct method, more studies used the analysis of artefacts as an assessment method compared to the Multiple Choice Questions (MCQ) /short answer test. Among analysis of artefacts, most studies analyzed log files/chat/multimedia posts as artefacts followed by written arguments and video/audio recordings of interactions. Also, regarding MCQ/short answer tests, a majority of studies used achievement and conceptual understanding tests to assess student performance. Future studies need to use embedded assessment tools in their platform to increase learning opportunities for students. Also, future studies should enable synchronous and asynchronous access for teachers to student activities for proper assessment.