This research aimed to elucidate effects of an essential oil (EO) supplementation including thymol, limonene and carvone as main active compounds on parameters of feed efficiency (FE) in early lactating Simmental cows. Two balanced groups of cows (n = 16) were used. The EO group received a total mixed ration (TMR) and a concentrate plus 0.56 g EO blend per kg of dry matter (DM), the control group (CON) was fed the same feed without EO dietary supplementation. Results showed higher DM intake (DMI) of TMR and daily milk yield for CON (22.48 and 39.17 kg) than for EO cows (21.03 and 37.10 kg, P < 0.001), while intake of the concentrate and FE (milk yield/DMI) did not differ. FE was increased as an effect of EO supplementation (1.84 vs 1.80, P = 0.001), if body weight and pre-experimental FE were respected as co-variates. The FE progress during the 4-week test period displayed a strong negative correlation of trend line slopes and intercepts (r = −0.887, EO group). An inherent FE of 1.69 separated the predicted FE progress by treatment. EO cows with a higher inherent FE proceeded in steeper FE slopes than CON. No evidence of a general increase of FE after EO intake in dairy cows could be determined, unless additional individual parameters are considered.