Our objective was to investigate Lactobacillus buchneri as a silage additive and the forage:concentrate (F:C) ratio on growth performance and meat quality of finishing beef cattle. The trial was a 2 (corn silage untreated or inoculated with L. buchneri) × 2 (two F:C ratios, 60:40 or 40:60) factorial. Bulls fed a 40:60 F:C diet containing inoculated silage had greater dry matter (DM) intake (P < 0.01) and average daily gain (P = 0.029) compared with other treatments. DM (P = 0.02) and neutral detergent digestibility (P < 0.01) were depressed by inoculation of corn silage with L. buchneri. Thiobarbituric acid concentration in meat increased (P < 0.01) by 15% in bulls fed the 60:40 F:C diet compared with the 40:60 F:C diet. Inoculation of silage increased (P = 0.02) the ratio of unsaturated fatty acids to saturated fatty acids. Compared with the 60:40 F:C diet, the concentrations of polyunsaturated fatty acids (P = 0.03) and omega-6 fatty acids (P = 0.02) increased in longissimus muscle by 23% and 26%, respectively, in bulls fed the 40:60 F:C diet. Inoculation of corn silage with L. buchneri inconsistently improved the growth performance and meat traits of finishing bulls consuming diets differing in F:C.