High-temperature laser scanning confocal microscopy (HT-LSCM) represents an excellent in-situ technique to observe austenite grain growth at elevated temperatures. In manufacturing processes, the grain size represents an important material parameter, especially for surface defect sensibility during continuous casting. Controlling the austenite grain size in further production steps determines the workability, process route and overall energy consumption to achieve the required product demands. Elements like niobium, phosphorus or even manganese tend to segregate on grain boundaries and inhibit grain boundary movement. This effect is well known as solute drag and can be indirectly characterized using HT-LSCM, enabling to provide accurate data for physical modelling of grain growth under isothermal and non-isothermal conditions. The present work focuses on the influence of carbon and phosphorus on the grain boundary movement of γ-Fe and summarizes selected results in the temperature range of 1050 - 1350 °C depending on initial C and P contents.