Under this research study, determined were the degrees of hydrolysis and oxidation of the fats contained in oilseeds, in seeds isolated from the bread studied (those seeds constituted a bread additive), as well as of the fats contained in the bread crumb. In addition, determined was the composition of fatty acids in the fat from the bread crumb. The research material, originating from the same bakery, comprised: 5 samples of oilseeds (sunflower, soybean, pumpkin, linseed, and sesame) and 7 kinds of bread (one without oilseeds added and six with oilseeds added). In the fat extracted from the initial oilseeds and isolated from the bread and bread crumb, the following was determined: values of acid, peroxide, and anisidine, contents of dienes and trienes, and fatty acid composition. It was found that the fat from oilseeds (raw material) contained low amounts of free fatty acids (FFA) and peroxides, but high amounts of secondary oxidation products. The baking process caused the degrees of lipid hydrolysis and oxidation in the oilseeds to increase; and the extent of this increase was essentially higher in the case of seeds scattered over the bread’s surface. Compared to the seeds from the bread crumb, the linseeds from the bread crust contained more than a double amount of peroxides, and the content of secondary oxidation products therein was over three times higher. Compared to the fat in the bread with no additives, the fat in the bread crumb with oilseeds was characterized by a lower acid values, a lower anisidine value, lower contents of dienes and trienes, and, in the majority of cases, a lower peroxide value. The addition of oilseeds was found to beneficially decrease the content of saturated fatty acids and to increase that of unsaturated fatty acids. The research results suggest that oilseeds should be added to bread dough instead of scattering them over the bread’s surface.