The commercial Nigerian peanut cultivars Ex-Dakar, Samnut-22 and Samnut-26, the Egyptian cultivar Ismailia-1 and the American cultivar NC-7 were genetically differentiated and the cultivars’ effects on growth and yield components, total lipid contents, including saturated and unsaturated fatty acids, and oil body size and number were investigated. Experiments were carried out at Cairo University Research Station, Giza, Egypt, during the summer seasons of 2016 and 2017. All cultivars had high contents of total unsaturated fatty acids and low contents of saturated fatty acids. Variations among tested cultivars in oil body size and number were documented and cultivars were ranked based on their oil bodies’ size as Ismailia-1 > Samnut-26 > NC-7 > Ex-Dakar ≥ Samnut-22. Oil body size and number were inversely related. This variation can be explained by the different amounts of acidic amino acids and the protein structure on the surface of the oil bodies of these cultivars. The distributions of protein bodies and oil bodies seemed to be negatively correlated. Cultivar effect was significant, and variation was found in seed production and quality in addition to the size and number of oil bodies, oil productivity, and oil quality among cultivars. Seasonal effects were not evident due to the stability of the climatic conditions during the two seasons of the study.