We report for the first time, to the best of our knowledge, regenerated polymer optical fiber Bragg gratings (RPOFBGs) in ZEONEX-based polymer optical fibers (POFs). The regeneration temperature can be adjusted using a heat treatment process on the POF before FBG inscription, enabling a scalable improvement of the thermal stability of the RPOFBGs. Thermal sustainability of the RPOFBGs at high temperature conditions was investigated for their prolonged use in diverse environments. Furthermore, these RPOFBGs can withstand strain levels up to 2.8% while maintaining a good linearity, even at temperature of 110°C. The RPOFBGs are capable of short-term operation at elevated temperatures of up to 132°C, which is the standard temperature for steam sterilization with at least a 4 min exposure period. The distinction in the morphologies of the two grades of ZEONEX (E48R and 480R, ZEON Corp.) used to fabricate the optical fiber together with the characteristics of UV irradiated and regenerated gratings is explained using micro-Raman spectroscopy. Collectively, these findings provide new heights for long-term operation of POF Bragg gratings (POFBGs) at elevated temperature environments and would be applicable to a wide range of disciplines.