Korean laws require labeling for genetically modified (GM) food ingredients. But the labels exempt oils made from GM soybeans because they contain no genetic elements after being processed. Previous literature has documented willingness to pay (WTP) for various foods with GM labels. However, most studies used surveys and ignored the potential effects of food origins and labeling exemptions for highly refined GM foods. This paper is to explore consumer preferences and estimate willingness to pay for GM and non-GM soybean oils. For our research, we used the random nth price auction mechanism targeting a total of 73 consumers living in Seoul and metropolitan areas. The experiment consisted of sequential five rounds where each round built up accumulated information regarding the presence of GM ingredients, potential effects, the country of origin, and stricter labeling requirements. The study results revealed that consumers were willing to pay 18% more for non-GM oils, 28% more for domestically grown soybean ingredients, and 38% more for oils under full disclosure labeling rules. The findings by a random effect model indicated that the prior awareness of GM labels and the level of education were significant determinants of the willingness to pay.