Extrusion cooking plays crucial role in the production of extrudate products from variety of flours such as grains, legumes, and tubers. This study focuses on optimizing extrusion cooking conditions for producing oat based extrudate snack from a composite flour of oats, potatoes, and chickpeas using a twin - screw extruder. The two key parameters investigated for optimization were the extrusion barrel temperature (ranging from 100 to 150°C) and blending ratio (with oat flour ranging from 40 to 80% and chickpea and potato flour ranging from 10 to 30%) at constant screw speed (350 rpm) and feed moisture content (22%). The study involved evaluating the proximate composition and functional properties of raw materials and blended flour, followed by extrusion cooking of the blended flour and evaluated the proximate, functional and physical properties of the extrudate product. Analysis of dependent variables was conducted using standard methodologies and analytical processes. The optimized extrudate snack was achieved at a barrel temperature of 125°C, with a blending ratio of 60% oat, 30% potato, and 10% chickpea flour. Under these conditions, the extrudate exhibited favorable characteristics, including 15.95% protein, 2.82% fat, 5.23% moisture, 4.12% fiber, 2.51% ash, and 74.13% total carbohydrates. Additionally, the extrudate showed optimal values for expansion ratio (2.35 mm/mm), water absorption index (6.58g/g), bulk density (0.28 g/cm3), and hardness (22.15N). Sensory evaluation of the snack extrudate produced under these conditions also indicated high ratings for color (6.36), appearance (6.25), crispiness (6.4), flavor (6.30) and overall acceptability (6.2). The developed linear model can serve as a valuable tool for predicting extrusion conditions to produce extrudates with desirable physical and functional attributes. Key words: Chickpea, Common oat, Extrusion, Gluten-free, Ready-to-eat snack