The present study was conducted to determine the effects of formulated feed (IRG: Italian ryegrass, WCC: whole crop corn, and fermented feed) on growth performance, carcass characteristics, and meat quality of Hanwoo steers during early and late fattening periods. Twelve Hanwoo steers were randomly assigned into two groups: control and treatment (n = 6/group). The control group received rice straw with concentrate; the Treatment group received formulated feed for 13 months. Results revealed that formulated feed supplementation significantly (p < 0.05) increased effects on dry matter (DM) intake, body weight, average daily gain, and carcass yield than control feed. Hanwoo steers fed formulated feed showed higher meat quality, carcass yield, and ribeye area than steers fed control feed. However, meat quality characteristics (such as cooking loss, fat thickness, marbling score, meat color, and crude fat), sensory characteristics, and pH values were similar between the two groups (all p > 0.05). There was no significant difference in FA compositions of steers between the two groups (p > 0.05). Overall, these results indicate that feeding Hanwoo steers with formulated feed can improve their growth efficacy, carcass yield, and meat quality characteristics during early and late fattening periods. Regarding an economic strategy, our research findings suggest that formulated feed is effective and profitable for feeding Hanwoo steers during early and late fattening periods without causing adverse effects.