A random search modeling approach is introduced to retrieve the thermal histories of magmatic bodies from chemical and isotopic analyses of olivine crystals. The sample used for demonstration is an olivine phenocryst from Kilauea Iki lava lake, Hawaii. Random time-temperature (t-T) paths were used to model diffusion accompanying crystal growth. Although a large number of t-T paths yielded acceptable fits to the Mg/Fe chemical profiles measured in olivine, only a small fraction resulted in acceptable fits to the Mg-Fe isotopic profiles. The best-fit cooling path was close to the independently inferred cooling history of this sample. Use of isotopic profiles in minerals coupled with a random search method can be a powerful tool for recovering thermal histories of rocks with little geologic context.