The present study evaluated the incorporation of red pitaya powder into a rice/chickpea (80:20) matrix, resulting in four treatments, namely T-2.5 (2.5%), T-5.0 (5.0%), T-7.5 (7.5%), and T-10 (10%) powder addition, which were processed through extrusion cooking, followed by microwave expansion for the development of a third-generation (3G) snack. The physicochemical properties, including expansion index (EI), hardness, and bulk density (BD), as well as functional parameters such as total polyphenol content (TPC) and antioxidant activity (AA), were analyzed. Furthermore, structural modifications generated by processing were examined via X-ray diffraction, FT-IR spectroscopy, and microstructural analyses. The addition of pitaya powder significantly affected the physicochemical properties of the 3G snacks, resulting in a decrease in EI, BD, and hardness after the extrusion and expansion process using microwaves. In addition, the bioactive potential of the snacks improved, generating the highest levels with the addition of pitaya powder, resulting in a 38% increase in TPC and a 3.1-times increase in AA, with a retention of 30% in total betalain content (TBC). Microstructural analyses showed modifications after processing, with a loss of crystalline order and transitions in the type-Ⅴ diffraction pattern, indicative of amylose–lipid complex formation, characterized by a decrease in the 1047/1022 ratio and stability of 1022/995 ratio. Also, the sensory analysis revealed that the 7.5% formulation was the most attractive, maintaining the principal characteristics of color and texture, with a general acceptance above 38%. These results demonstrate that the incorporation of pitaya powder enhances the bioactive, functional, and sensorial properties of third-generation extruded products.