This work describes the physical property analysis and molecular structural characterization by gas chromatography and nuclear magnetic resonance spectroscopy of cottonseed, sunflower, corn, canola, and soybean oils. To assess the relative quenching performance of these different vegetable oils, cooling curve analyses was conducted according to ASTM D6200 at series of quenchant bath temperatures: 40, 60, 80, 100, and 120°C. For comparison, cooling curve analysis under the same testing conditions for a commercially available conventional and an accelerated petroleum oil-based quenchant was also performed. This work showed that although the different vegetable oils exhibited significantly different molecular structures, their viscosity and viscosity-temperature behavior was comparable. Also, the quenching performance of the different vegetable oils, while not identical, was not significantly different from each other. However, it is noteworthy that the vegetable oils did not exhibit classical film boiling or nucleate boiling behavior during quenching. For this reason, the quenching performance was different from either the conventional or the accelerated quench oils, which exhibited the expected film boiling, nucleate boiling, and convective cooling behavior. The relative difference in quenching performance between petroleum oil derived quenchants and vegetable oils is discussed in detail.