<p>The increasing prevalence of oat-based milk substitutes in the market has led to the generation of a substantial volume of β-glucan-enriched oat by-products (OBP) during production. However, the high moisture content of OBP poses challenges, as it is prone to decay and deterioration, making it difficult to recycle and reuse. This study aimed to pre-treat OBP using various drying methods and incorporate different ratios of brown rice with OBP in the extrusion process. The goal was to examine the effects of these variables on the physicochemical properties, textural characteristics, and digestibility of extruded snacks. Results showed that dried OBP was successfully incorporated into brown rice-based extruded snack formulations at levels of 5–15%. The radial expansion ratio (ER), bulk density (BD), and fracturability exhibited a negative correlation with the incorporation percentage, whereas hardness showed a positive correlation (<i>p</i> &lt; 0.05). Additionally, the β-glucan and resistant starch (RS) contents of the extruded snacks increased significantly with higher OBP incorporation. The glycemic index (GI) of the extruded snacks decreased significantly, from 83.51 to 75.35, as the OBP content in the formulation increased. However, the sensory evaluation results showed that the consumer-based panelists agreed to incorporate 5% freeze-dried (FD) or complex drying (CD; autoclaving combined with hot-air drying) OBP into the extruded snacks. This study emphasizes the importance of carefully selecting incorporation ratios and employing suitable drying pre-treatments to achieve optimal sensory characteristics in extruded snacks.</p>