Understanding how sandy barrier systems respond to projected sea-level rise and increasing storm intensity is critical for coastal hazard assessment and shoreline management. Despite the increasing global interest in barrier dynamics, the Australian barrier system washover record remains inadequately constrained. This is largely attributed to their long-term geomorphic stability Holocene timescales and relatively rare occurrence of large-scale overwash events along this tectonically stable, wave-dominated coast. This study addresses that gap by investigating the morphostratigraphy and chronology of Holocene washover deposits along the southern New South Wales (NSW) coast, with a focus on barrier systems at Merimbula. A multi-proxy approach was adopted, integrating high-resolution LiDAR-derived topography, historical shoreline changes datasets form DEA Coastlines, satellite imagery from Nearmap and Planet Labs, and detailed sedimentological analyses, this study aims to identify and characterise washover landforms and their spatial extent. Sediment cores collected along shore-perpendicular transects were examined for facies architecture and subjected to optically stimulated luminescence (OSL) dating to establish depositional timing and reconstruct discrete phases of barrier overwash within a mid- to late-Holocene sea-level context. The results reveal distinct stratigraphic signatures associated with storm-driven overwash events and demonstrate temporal variability in barrier response linked to fluctuations in relative sea level, wave climate, and sediment supply. This results also provide a new insight into overwash processes in a wave-dominated, microtidal setting where such events are relatively uncommon, and offer valuable implications for predicting future coastal change and enhancing barrier resilience under accelerating sea-level rise.