The present study evaluated the effects of feed supplementation with olive oil by-products on the microbial quality of rabbit meat. Thirty-three New Zealand White rabbits were randomly assigned to three experimental grower–finisher diets. Each dietary group consisted of three experimental treatments: (1) a basal control diet (C), (2) a C diet supplemented with a low dosage of polyphenol (150 mg/kg, L), and (3) a C diet supplemented with a high dose of polyphenols (280 mg/kg, H). Polyphenol analyses in feed and meat were performed using the liquid-chromatography coupled to tandem mass spectrometry technique (LC-MS/MS). Higher amounts of sulphate metabolites were detected in the H group. Microbiological quality was evaluated on Longissimus lumborum muscles stored under aerobic conditions at 4 °C. The H diet exerted an inhibitory effect on microbial growth (p < 0.001), notably for Pseudomonas spp., when compared to C and L diets; differences among the groups were observed starting from 6 days of storage. In the H group, the Pseudomonas spp. population showed an increase in the latency phase and a decrease in the maximum growth rate of the fitted curves in comparison with the C and L groups. The use of dietary polyphenols could be a strategy to reduce spoilage during meat storage.