The objective of the present study was to investigate live weight (LW) gain, urinary nitrogen (UN) excretion and urination behaviour of dairy heifers grazing pasture, chicory and plantain in autumn and spring. The study comprised a 35-day autumn trial (with a 7-day acclimation period) and a 28-days spring trial (with a 7-day acclimation period). For each trial, 56 Friesian × Jersey heifers were blocked into five dietary treatments balanced for their LW and breeding worth (i.e. genetic merit of a cow for production and reproduction): 1·00 perennial ryegrass–white clover pasture (PA); 1·00 chicory (CH); 1·00 plantain (PL); 0·50 pasture + 0·50 chicory (PA + CH); and 0·50 pasture + 0·50 plantain (PA + PL). A fresh allocation of the herbage was offered every 3 days with allowance calculated according to feed requirement for maintenance plus gain of 1·0 kg LW/day. In both trials, LW gain was lower on CH than other treatments. In the spring trial, UN concentration and UN excretion were lower in CH and PL than other treatments. In autumn, a higher urination frequency was observed over the first 6 h after forage allocation in CH and PA + CH than other treatments. Data from the present study indicate that feeding CH alone limited heifer LW gain. However, heifers grazing swards containing chicory (CH and PA + CH) and plantain (PL and PA + PL) had the potential to lower nitrous oxide emissions and nitrate leaching from soil compared with heifers grazing PA, by reducing N loading in urine patches.