One hundred twenty-eight crossbred steers (initial BW 720.0 ± 10.4 lbs.) were used to compare conventional vs. natural feeding practices on steer performance, carcass characteristics, and cost of production. Cattle were allotted by weight and source to one of four diets: a conventional 85% concentrate diet containing Rumensin® (Elanco Animal Health, Greenfield, IN) (C85), and three natural diets (N85, N70, and N55) at respective concentrate levels of 85, 70 and 55% containing Bovi-Sacc® (Alltech; Nicholasville, KY). The concentrate portion of the diet consisted of dry-rolled barley and peas, the roughage portion of the diet consisted of oat hay and corn silage. Cattle were fed at the Carrington Research Extension Center (CREC) in 16 open drylot pens (8 steers per pen; 4 pens per treatment), and were slaughtered when body weight for the treatment was estimated to be 1175 lbs. Slaughter weight did not differ among treatments (P > 0.40). Steers fed the C85 and N85 diets spent the least (P < 0.01) amount of time in the feedlot (154 days), and gained the fastest (P < 0.01, 3.07 and 2.93 lbs./d, respectively). Steers fed the N55 diet spent the most amount of time in the feedlot (210 days), and gained the slowest (2.26 lbs./d). Cattle fed the N70 diet spent an intermediate amount of time in the feedlot (180 days) and gained 2.51 lbs./d. Steers fed the N55 diet were the least efficient (P < 0.01). Cattle fed the N85 and C85 diets were the most efficient (P < 0.01). Hot carcass weight did not differ among treatments (P > 0.15). Marbling score tended to be greater (P = 0.06) and fat thickness was greater (P < 0.01) for cattle fed the C85 and N85 diets. Ribeye area tended to be greatest (P = 0.07) for cattle fed the N85 diet and lowest for cattle fed the N55 diet. Yield grade tended to be greatest (P = 0.06) for cattle fed the C85 diet, and lowest for cattle fed the N70 diet. Feed cost per cwt of gain was $36.00, $37.66, $42.55, and $44.63 for cattle fed the C85, N85, N70, and N55 diets, respectively. To profitably raise beef without ionophores, producers can use Bovi-Sacc in the diet which was effective in the 85% concentrate diet. Lower energy diets would require a premium price for the animals for equal income.