The physiological status and productivity of beef cattle in tropical regions are influenced by their adaptation to hot and humid environments. This study aimed to measure and compare the physiological and behavioural characteristics of Ongole-cross and Simmental-cross breeds and examine their correlation with environmental temperature. Physiological indicators, including rectal temperature, breathing rate, and pulse frequency, along with the duration of specific activities such as locomotion, lying, eating, and rumination, were systemically collected from five male Ongole-cross and five male Simmental-cross cows. Based on the calculation of the average temperature humidity index (THI), all cows experienced moderate environmental stress. As homeothermic animals, rectal temperature did not correlate with ambient temperature in both breeds. Conversely, a strong correlation between respiration rate and environmental temperature was measured in both both breeds. In addition, the correlation between pulse rate and environmental temperature was strong and weak in Simmental-cross and Ongole-cross breeds, respectively. Both breeds exhibited a significantly longer duration of rumination during the night than during the daytime. Notably, the Ongole-cross breed displayed an extended duration of eating during the daytime. In conclusion, the Simmental-cross breed demonstrated a more robust physiological and behavioural responses, indicating their thermoregulatory compensation under a moderate environmental stress.