Wheat flour supplemented with 5, 10, 15, 20 and 25% sorghum flour and sourdough bread made thereof were evaluated for mineral contents, phytic acid, tannin, total phenols and in vitro protein digestibility. Effect of supplementation was assessed on nutritional quality of the sourdough flatbread. Analyses of the sorghum supplemented flours revealed a significant (p<0.05) increase in crude fat(%), crude fiber(%) and NFE (%)with a decreasing pattern in crude protein and ash contents. Sourdough fermentation appeared to improve mineral contents in bread since the concentration of iron, zinc and manganese were increased from 3.07-4.41, 0.87-0.95 and 2.48-2.56 mg/100 g, respectively. Phytic acid (%) and tannin (%) were reduced from 1.14 to 0.57, and 0.40 to 0.22, respectively in flatbread. Total phenols of composite flour decreased from 342 to 104 mg/100 g in sourdough flatbread. Similarly, in vitro protein digestibility was shown to increase from 74.81 to 81.14% apparently due to reduction in concentration of chelating agents by fermentation process. Conclusively, composite flour technology in combination with lactic acid fermentation was found quite successfully exploited to reduce anti-nutritional compounds, enhance availability of minerals and improve the digestibility of non-conventional cereal grains.