Beef patties are highly consumed worldwide. However, its formulations often include synthetic antioxidants and antimicrobials. Murtilla (Ugni molinae Turcz.), a shrub native to southern Chile, has leaves with a polyphenolic concentration 3.2 times higher than its fruits. This study evaluated the effects of three concentrations of murtilla leaf powder (500, 1000, and 1500 mg/kg) on the microbiological, physicochemical, and sensory parameters of beef patties, compared to controls without antioxidants and with erythorbate (500 mg/kg). The patties were stored at 2 degrees C for 12 days in a modified atmosphere (80% O-2/20% CO2). No changes were observed in proximal composition; however, the 1500 mg/kg concentration affected the redness (a*) of the beef patties (15.04 vs. 19.37 in the control) (p <= 0.05). Oxidative stability increased as follows: Mu1500 (88.21%) > sodium erythorbate (83.5%) > Mu500 (79.7%) > Mu1000 (78.8%). Natural antioxidants decreased the deterioration of essential fatty acids such as linoleic acid. Aerobic mesophilic microorganism growth in the murtilla treatment was lower than in the control (2.06 log cfu/g vs. 3.83 log cfu/g). Murtilla leaf powders show promising results as a substitute for synthetic antioxidants and antimicrobials. Mu500 treatment improved the physicochemical and microbiological quality parameters without compromising the sensory characteristics.