Background and Objectives: Flat breads are the most consumed bread in Iran. Barbari one of the popular ones, is traditional flat leavened Iranian bread and one of the most popular breads consumed in Iran and some other countries in the Middle East. Materials and Methods: The aim of this study was to evaluate the effect of substitution of wheat flour by whole quinoa flour (0-15% substitution) and xanthan gum (0-1.5%) on quality properties of Barbari bread. The effects of whole quinoa flour and xanthan gum additions on bread preparation and bread quality parameters such as specific volume, textural characteristics, image processing, differential scanning calorimetry (DSC), scanning electron microscope (SEM) were determined by Response Surface Methodology (RSM) using a central composite design. Results: The results showed that the addition of quinoa flour decreased specific volume, porosity and increased firmness, but addition of xanthan increased springiness. According to the results, optimized sample was selected of the 9.1 % quinoa flour and 1.25 % xanthan gum. Then, structure of starch granules, enthalpy, crude fiber and mineral content of optimized and control samples were evaluated. Results showed that crude fiber and mineral content of optimized sample were increased as compared to control bread. In spite of that, the enthalpy of fortified sample was higher. Conclusions: Due to appropriate nutritional value of quinoa flour and proper effect of xanthan on texture, therefore this ingredient could be used as substitute for wheat flour in Barbari formulation.