Abstract The objective of the present study was to compare the synchronisation of the lying, feeding and standing behaviour of bulls housed in an uninsulated barn and in a pasture. Dairy (Ayrshire and Holstein-Friesian) and beef (Hereford) bulls were housed in June-July in either partly bedded pens in an uninsulated barn (PEN bulls; five groups of four or five bulls with 6.4 or 8.0 m2/bull) or in a pasture (PAS bulls; five groups of four or five bulls with 680, 1000 or 1250 m2/bull). The PEN bulls were fed grass silage ad libitum. For concentrate supplementation both the PEN and PAS bulls received rolled barley 4.4 kg dry matter/animal/day. The behaviour of the bulls was observed for two 24-h periods. The animals were 15–17 months old during the observations. Instantaneous sampling with a 6-min sampling interval (IS-6 min) was used originally for collecting the data. Lying, eating and standing (=all other activities performed in a standing posture) were recorded during the IS-6 observations. The Fleiss’ Kappa coefficient was used as an index of behavioural synchronisation. It was calculated for each of the groups of four or five animals across 24 (IS-60 min) and 12 (IS-120 min) time points within a 24-h day to increase the independency of the data points. The Fleiss’ kappa coefficient was calculated in two ways: combining all three behavioural classes of each observation day (KFO) as well as separately for lying (KFL), eating (KFE), and standing (KFS). The results were analysed using a selected multilevel linear mixed model. The IS-60 min (presented in the abstract) and IS-120 min results were essentially identical. PAS bulls displayed more synchronised behaviour than the PEN bulls (P