Oat (Avena sativa L.) by-products are valuable sources of many bioactive compounds and minerals. This paper aimed to study the possibility of using micronized oat husk (hull) as a partial replacement for wheat flour (at levels 5, 10, 15, and 20%) in shortbread production. The physicochemical and sensory properties of control and enriched cookies were studied. The incorporation of oat husk into shortbread increased the fiber and ash content, and decreased the available carbohydrates in the cookies. The color of the enriched shortbread significantly changed and the total color difference between the control and enriched cookies ranged from 4.76 to 11.00. Moreover, the total phenolics content and antioxidant activity linearly increased with the percentage of husk in the cookie recipe. Importantly, micronized oat husk at a level of 20% had little influence on the sensory acceptability of cookies. However, replacement of wheat flour higher than 10% resulted in a harder texture of cookies and lower scores for this attribute were obtained. To summarize, in this work we showed that micronized oat husk can be a valuable additive for cookie fortification.