In grazing dairy farming systems measurement of feed intake is problematic, especially due to lack of practical methods to determine the quantity of pasture that cows graze. Our aim was to measure relative DM intake by grazing behavior using tri-axial accelerometers. Tri-axial accelerometers (ActiGraph) were set to continuous recording at 60 Hz and attached to collars around the neck of 10 lactating dairy HF and HF-Jersey cross cows (HF 82.5% to 100%) on a commercial dairy herd in Northern Victoria, Australia. After 16 full days of recording, the sensors were removed from the collars and recorded RAW data downloaded from the sensors. The 16 d RAW data were used to determine grazing time, bites and intensity. Occasional observational data of cow behavior was used to validate behavior of cows as determined from the activity counts. All cows in the herd were offered the same ration (flat-feeding), consisting of approximately 1/3rd of DM as concentrate and 2/3rd of DM as forage. Forage was predominantly grazed pasture. Herd test results during the trial provided data regarding milk production and somatic cell count (SCC) of individual cows. The data set (n = 10) showed AVG per day grazing time of 340 min (265 to 397), 21,390 grazing bites (16,409 to 25,810) and 541,957 counts for grazing intensity (345,094 to 641,808). Two cows had a high SCC (>2,500,000/mL), indicating subclinical mastitis, and were excluded from the data set used for correlations. The cows (n = 8) had an AVG daily milk yield of 30.6 L (17.7 to 39.1) and 108 d in lactation (62 to 134). The correlation between number of daily bites and daily milk yield was R2 0.80, while grazing time (minutes per day) had a correlation to milk yield of R2 0.69. These results suggest that tri-axial accelerometer sensors are useful in determining grazing behavior of lactating dairy cows.