This study was conducted to develop high-functional, gluten-free plant-based meat patties using Phellinus linteus HN009K mycelium-cultured oats (PMO) and to investigate their quality characteristics. The results showed that the crude protein content of PMO increased by approximately 14.4% compared to the uncultured control (UCO). Notably, the β-glucan content exhibited a significant 3.9-fold increase, demonstrating a synergistic effect between the mushroom mycelium and the oat substrate. Texture Profile Analysis (TPA) revealed that as the PMO content increased, the hardness of the patties decreased, providing a tender mouthfeel, while the chewiness was significantly enhanced compared to the control, successfully mimicking a meat-like texture. Furthermore, the patties containing 20% PMO showed significantly improved antioxidant activity and maintained the immune-active components derived from P. linteus. In conclusion, PMO is a promising core material that simultaneously enhances the nutritional value and textural properties of plant-based meat analogs. These findings provide foundational data for the development of high-value-added alternative protein foods.