To investigate the immediate and long-term effect of once-daily milking during early lactation on milk production and DMI in a pasture-based dairy system, 20 primiparous Holstein dairy cows were assigned to 2 treatments (n = 10), in a randomized complete block design, from d 3 postpartum and for 8 consecutive wk of lactation (treatment period): once-daily milking (1x) or twice daily (2×). After this period all cows were milked 2× until wk 43 of lactation (all lactation). Cows were fed by grazing oats (Avena sativa) and supplementation with a TMR (30:70, DM basis). Individual milk yields were recorded every day and milk composition was determined in 2 consecutive milkings each wk. The TMR intake was determined by weighing the amounts offered and refused. Pasture intake was estimated as the difference between pre and post-grazing pasture mass, using a rising plate-meter previously calibrated. Data were analyzed using the SAS MIXED procedure, and the treatment and treatment × wk effects were tested. Total DMI (18.9 ± 0.56 kg DM/d), pasture and TMR intake were not different (P < 0.10) between treatments. Milk yield was lower in cows milked 1× during the treatment period (15.3 vs. 24.9 ± 0.53 kg/d) and a carryover effect was observed until 21 wk of lactation, with interactions treatment × wk, for both periods (P < 0.001). Milk yield for the entire lactation was decreased by 14.9% (P = 0.018) in the 1× group. Lactose concentration was lower in cows milked 1x (4.88 vs. 5.03 ± 0.04, P < 0.001) decreasing 16% total lactose yield (P = 0.007). Total protein yield decreased by 12% in cows milked 1× (P = 0.005) and milk protein concentration was affected in the 1× group (3.36 vs. 3.29 ± 0.03, P = 0.004). Milk fat concentration was higher for 1× during the treatment period (4.83 vs. 3.74, ± 0.21, P < 0.001), but fat yield did not differ. Cows milked 1× during the first 8 wk of lactation tended to have a lower total milk solids yield by 10.4% until wk 43 (P = 0.052). In conclusion, once-daily milking during the first 8 wk of lactation in primiparous dairy cows did not affect DMI, but had immediate and carryover negative effects on milk and milk solid yields.