Genetic selection on feed efficiency could increase the profitability of French beef farms. The BEEFALIM 2020 project aims to study the genetic determinism of this trait measured from 2016 to 2019 on 588 young Charolais bulls in four experimental farms. After weaning in commercial farms, the young bulls entered the fattening barns at 303 (±26) days of age and were fed ad libitum either with grass or corn silage. During the 29 (±3) weeks of the test period, dry matter intake (DMI) was recorded daily and animals were weighted every 14 days. Average daily gain (ADG) and final body weight (FW) were calculated using regression of body weight on time. Three feed efficiency criteria were used: residual feed intake (RFI), residual gain (RG) and feed conversion efficiency (FCE). Genetic parameters were estimated using WOMBAT software with an animal model containing the contemporary group as fixed effect, age at the start of the test as covariate and farm origins × year, genetic and residual as random effects. During the test period, DMI averaged 9.65 (±1.13) kg/day, ADG 1.51 (±0.29) kg/day and FW 698 (±74) kg. The three traits were closely correlated phenotypically: 0.67 between FI and ADG, 0.77 between FW and ADG and 0.82 between FI and FW. Feed intake and ADG were more heritable (0.34) than FW (0.20). The three feed efficiency traits were moderately heritable (0.22 for RFI and RG; 0.18 for FCE). No genetic correlation was found between RFI and RG or FCE while a strong genetic correlation of 0.99 was estimated between RG and FCE. Residual feed intake was genetically correlated with DMI (0.82), ADG (0.52) and FW (0.49). Both RG and FCE were closely correlated with ADG (0.79 and 0.75, respectively) and moderately with DMI (0.31 and 0.23, respectively) or FW (0.33 and 0.25, respectively). Even if RFI and RG were phenotypically independent with traits used in both regressions, genetic relationships were found between them. Genetic improvement is possible through a selection index combining both feed efficiency and production traits.