Ruminants fed high-forage diets usually have a low feed efficiency, and their performances might be limited by methionine (Met) supply. However, the INRA feeding system for growing cattle do not give recommendation for this amino acid (AA). This study aimed to assess the effects of Met-balanced diets on animal performance and N metabolism in young bulls fed high-forage diets formulated at or above protein requirements. Four diets resulting from a factorial arrangement of two protein levels (Normal [13.5% CP] vs High [16.2% CP]) crossed with two Met concentrations (unbalanced [2.0% of metabolizable protein] vs balanced [2.6% of metabolizable protein]) were tested on 34 fattening Charolais bulls for 7 months before slaughter. Animal growth rate was greater in Met-balanced diets (+8%; P = 0.02) with a trend for a greater impact in High vs Normal protein diets (P = 0.10). This trend was observed in lower plasma concentrations of branched-chain AA only when Met supplementation was applied to Normal protein diet (P ≤ 0.06) suggesting another co-limiting AA at Normal protein level. Feed conversion efficiency and N use efficiency were unaffected by Met supplementation (P = 0.05). However, some plasma indicators suggested a better use of AA when High protein diets were balanced vs unbalanced in Met. The proportion of total adipose tissue in carcass increased (+5 percent units; P = 0.03) whereas that of muscle decreased on average 0.8 percent units (P = 0.05) in Met-balanced diets. Our results justify the integration of AA into dietary recommendations for growing cattle.