Russula vinosa Lindblad is a traditional food and medicine resource with potential application in the field of functional foods, which is rich in polyphenolic compounds. In this study, the R. vinosa Lindblad was mixed fermented with Saccharomyces boulardii and Lactobacillus lactis and the antioxidant activity, composition and application in functional bread of the ethanol extract of the mixed bacterial fermentation product (EMFP) were investigated. The results showed that after fermentation, 186 new compounds appeared in EMFP, including organic acids and phenolic acids. The addition of EMFP significantly enhanced the quality and antioxidant activity of the bread, including reduction of hardness and chewiness, enhancement of resilience, and improvement of free radical scavenging activity and total reducing power. Furthermore, the EMFP addition affected color, odor, and texture indicators of the bread, and negatively affected at higher additions. 0.5% EMFP addition might be appropriate to positively affect the quality, sensory evaluation, and antioxidant activity of the bread. This study investigated the positive effects of mixed fermentation on the active ingredients of the R. vinosa Lindblad, providing a reference for the practical application of EMFP in the field of functional foods.