BACKGROUNDOleaster (Elaeagnus angustifolia L.) possesses exocarp and endocarp layers enriched with abundant phytochemicals and fiber. Flours produced in different parts of oleaster were used in cookie formulation to improve the bioactive components and nutritional properties of cookies.RESULTSThe rheological properties of composite flours containing varying levels of oleaster exocarp flour (O'EX‐F) and endocarp flour (O'EN‐F), ranging from 0% to 30%, were assessed using Mixolab (Chopin Technologies, Villeneuve‐la‐Garenne, France). The physical, chemical, nutritional, and sensory properties of cookies made with these flours were also analyzed. The substitution of O'EX‐F and O'EN‐F in the cookies enhanced redness and total color differences at the same time as decreasing hardness and improving the spread ratio. Furthermore, using these flours elevated the dietary fiber content of the cookies, particularly in terms of soluble and total dietary fiber. O'EX‐F and O'EN‐F also significantly increased free, bound, and total phenolic contents, as well as antioxidant capacity. Sensory evaluation of cookies with 10% and 20% O'EX‐F and O'EN‐F indicated greater appreciation than control cookies. Incorporating 20% O'EX‐F and 20% O'EN‐F into cookies resulted in a notable increase in Ca, Mg, K, Fe, and Zn levels.CONCLUSIONThe utilization of O'EX‐F and O'EN‐F, which contain a wealth of bioactive components, has significantly impacted the dough of rheology. Including these ingredients in cookie formulations has demonstrated improvements in ash, dietary fiber content, phenolics, antioxidant activity, and overall technological quality at the same time as providing distinctive sensory properties. The present study has contributed a new composite flour to the existing literature and has facilitated the development of novel cookie products for the functional food industry. © 2023 Society of Chemical Industry.