Oat has high nutritional value as it contains high proportion of protein, lipid and ?-glucan, along with a good amino acid composition. On the other hand, it is considered for diet in celiac disease and multiple sclerosis, due to its low gluten. In this study, starch and protein isolate were extracted from dehulled oat flour. The starch was modified using cross-linking and acetylation protocol whereas. Deamidation and succinylation were used to modify protein isolate. For starch, physicochemical properties such as swelling power, water binding capacity, gelatinization temperature and pasting properties and for isolated protein, functional properties such as emulsion activity and stability, foaming capacity and stability, nitrogen solubility index, water and oil binding capacity were measured in native and modified samples. Molecular weight of protein before and after modification was determined by electrophoresis. Cross-linking decreased swelling power of starch ( P 0.001) whereas water binding capacity ( P 0.001) and syneresis ( P 0.001) increased, but it has not significant effect on gelatinization temperature. Acetylation increased swelling power ( P 0.001) and water binding capacity ( P 0.001), but gelatinization temperature and syneresis ( P 0.001) diminished. Deamidation and succinylation increased emulsion activity ( P 0.001), foaming capacity ( P 0.001), nitrogen solubility index and water and oil binding capacity ( P 0.001), but emulsion stability didn’t change with deamidation and diminished with succinylation, while foaming stability ( P 0.001) decreased with both treatments. By substitution of oat flour with modified starch and protein, and physical properties of cake such as its batter viscosity, volume, color and staling were studied. Acetylated starch and two type of modified protein were selected because of their mentioned properties and were substituted in the level 5, 10, 15 and 20 percent of oat flour weight. The prepared cake of oat flour has lower batter viscosity ( P 0.001), higher volume ( P 0.001), darker color ( P 0.001) than those in wheat flour cake. Modified starch and protein isolates Acetylated starch increased batter viscosity ( P 0.001), cake volume ( P 0.001) and whiteness of crust ( P 0.05) of cake. Increasing in level of deamidated protein produced cake with lower batter viscosity ( P 0.001), higher volume ( P 0.001), darker color (decrease in whiteness and increase in redness ( P 0.001)), but increase in level of succinylated protein increased batter viscosity ( P 0.001) and lightness ( P 0.001) and decreased volume of cake. In compared with control cake, acetylated starch with deamidated protein isolate improved batter viscosity and volume. Therefore substitution of acetylated star