While Fibre-Reinforced Plastics are lightweight, show a high tensile strength, and have no issue with corrosion, they are unfortunately brittle and perform poorly against temperature. Therefore, it is important to know the time and magnitude of the temperature reaching the bars in the high-temperature effect of FRPs produced in the form of bar in reinforced concrete structural elements in concrete. This study set out to examine the time and temperature values of glass fiber reinforced polymer (GFRP) reinforced concrete under high-temperatures. The effects of concrete cover thickness and concrete strength on temperature transfer were researched experimentally. GFRP bars were placed in specimens prepared in three concrete strengths and three different concrete cover thicknesses (20-40-60 mm) exposed to temperature, and temperature-time graphs were created by measuring bar temperature, concrete surface temperature and ambient temperature. The critical time to a glass transition temperature, and optimum cover thickness of GFRPs according to concrete strength and concrete cover thickness were discussed. The study results appeared to indicate that the thickness of the concrete cover is very effective in protecting the bar against temperature in reinforced concrete structural elements, as concrete strength, itself, has only a limited effect.