Cold-formed Light gauge Steel Frame (LSF) walls lined with plasterboards are increasingly used in the building industry as primary load bearing components. Although they have been used widely, their behaviour in real building fires is not fully understood. Many experimental and numerical studies have been undertaken to investigate the fire performance of load bearing LSF walls under standard fire conditions. However, the standard fire time-temperature curve given in ISO 834  does not represent the fire load present in typical modern buildings that include considerable amount of thermoplastic materials. Some of these materials with high in calorific values increase the fire severity beyond that of the standard fire curve. Fire performance studies of load bearing LSF walls exposed to realistic design fire curves have also been limited. Therefore in this research, finite element thermal models of LSF wall panels were developed to simulate their fire performance using the recently developed realistic design fire time-temperature curves . Suitable thermal properties were proposed for plasterboards and insulations based on laboratory tests and available literature. The developed finite element thermal models were validated by comparing their thermal performance results with available realistic design fire test results, and were then used in a detailed parametric study. This paper presents the details of the developed finite element thermal models of load bearing LSF wall panels under realistic design fire time-temperature curves and the results. It shows that finite element thermal models of LSF walls can be used to predict the fire performance including their fire resistance rating with reasonable accuracy for varying configurations of plasterboard lined LSF walls exposed to realistic design fire time-temperature curves.