To develop a diet for Hanwoo steers during the late fattening phase, three different feeding treatments were investigated: a group fed concentrate and rice straw separately (Formula feed), a group fed TMR during the whole late fattening period (TMR), and a group fed TMR plus concentrate (Formula-TMR). Thirty Hanwoo steers 20 months of age (average body weight = 445 kg) were allotted by a completely randomized design into three treatment groups (ten steers in each group). The impact of these treatments on the performance, carcass traits, and blood composition related to body fat synthesis was assessed. The average dry matter and TDN intake were greater in Formula-TMR compared to other treatments (p<0.05); however, body gain, carcass weight, meat production index, and fat color were not affected by dietary type. Blood characteristics, such as concentrations of retinol, insulin, and leptin were not affected by any of the treatments; however the marbling score of the longisimus muscle was significantly higher in Formula-TMR (p<0.05), which was relatively high in blood leptin concentration. The muscle texture, meat quantity index, and meat quality index were highest in the Formula feed, TMR, and Formula-TMR, respectively (p<0.05).