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Forage nutrient quality and consumption have major impacts on ruminant production.� Energy requirements of the grazing animal are influenced by several factors such as increased foraging activity, frame size and physiological status, but is superseded by the requirement to maintain a homothermic balance. Therefore, we hypothesized that changes in grazing behavior activities would affect core-body temperature (CBT) and animal performance measures. A two-year study was conducted on 24 grass-finished cattle at the University of Hawaii, Mealani Agricultural Experiment Station. Animal behavior, CBT, weather variables, and forage quality were assessed during three daily observation periods (AM, NOON, PM) for the fall 2013, and summer and fall 2014 seasons. Over all seasons, active grazing (63.0%), standing (15.6%) and laying while chewing (10.4%) were the predominant behaviors observed.� Grazing activity across daily periods were highest during the AM period, a time when mean CBT (38.3�0.01�C) was lowest. The CBT varied for all animals across seasons and periods, and averaged 38.6 (�0.03)�C in 2013 and 38.4 (�0.04)�C in 2014.� We did not find any significant relationship between CBT and grazing behavior.� Forage quality varied seasonally, however crude protein (CP), relative feed value (RFV) and total digestible nutrients (TDN) were higher in summer 2014 compared to the fall seasons. Diurnal differences were observed in water-soluble carbohydrate (WSC) and non-fiber carbohydrates (NFC), which were higher in the PM across all seasons.� Average Daily Gain (ADG) was not significantly greater (P=0.78) between the years 2013 (0.58�0.06kg/d) and 2014 (0.56�0.05kg/d).� Animals were slaughtered at approximately 21(� 0.15) months of age and an average live body weight of 527.1 (�8.98) kg in both years. In 2013, 75% of the animals graded Choice or higher compared with 90% in 2014. The higher quality of forage in 2014 may have influenced beef quality.