Simple SummaryFermented feed is an effective way to replace antibiotics in poultry. The purpose of this study was to explore the effects of different levels of fermented feeds on growth performance, nutrient utilization, antioxidant function, meat quality, and intestinal microorganisms of broilers. The current research results showed that adding 10% fermented feed significantly improved the growth performance in 1–21 days, and adding 5% fermented feed significantly improved the growth performance in 1–42 days. Adding 15% fermented feed significantly improved the metabolic rate of the birds in 19–21 days and significantly increased the monounsaturated fatty acid concentration in the chickens. Adding fermented feed significantly reduced the cholesterol content in the chickens. In a word, adding 10% fermented feed significantly reduced the feed conversion ratio in 1–21 days and adding 5% fermented feed significantly improved the average daily gain and the average daily feed intake in 1–42 days. In addition, consuming fermented feed improved the meat quality of broilers.We investigated the effects of fermenting the plant fraction of a solid complete feed (FPFF) on the growth performance, nutrient utilization, meat quality, antioxidant status, and intestinal microbiota of broiler chickens. The plant-based fraction of the complete feed was fermented using Lactobacillus and Bacillus subtilis. A total of 240, 1-day-old male Arbor Acres broilers were randomly allocated into four treatment groups, each comprised of six replicates. The groups were fed a corn–soybean meal-based diet (basic diet) or the same diet supplemented with 5%, 10%, or 15% FPFF for 6 weeks. As results, adding 10% fermented feed significantly improved the growth performance in 1–21 days, and adding 5% fermented feed significantly improved the growth performance in 1–42 days. Adding 15% fermented feed significantly improved the metabolic rate of the birds in 19–21 days and significantly increased the monounsaturated fatty acid concentration in the chickens. Adding fermented feed significantly reduced the cholesterol content in the chickens. In conclusion, adding 10% fermented feed significantly reduced the feed conversion ratio in 1–21 days and adding 5% fermented feed significantly improved the average daily gain and the average daily feed intake in 1–42 days. In addition, consuming fermented feed improved the meat quality of broilers.