The majority of information concerning the cardio-metabolic performance of varanids during exercise is limited to a few species at their preferred body temperature (T_b) even though, being ectotherms, varanids naturally experience rather large changes in T_b. Although it is well established that absolute aerobic scope declines with decreasing T_b, it is not known whether changes in cardiac output (V_b) and/or tissue oxygen extraction, (C_aO₂ - C_vO₂), are in proportion to the rate of oxygen consumption (VO₂). To test this, we studied six Rosenberg's goannas (Varanus rosenbergi) while at rest and while maximally exercising on a treadmill both at 25°C and 36°C. During maximum exercise both at 25°C and 36°C, mass-specific rate of oxygen consumption (VO_{2 kg}) increased with an absolute scope of 8.5 ml min^-1 kg^-1 and 15.7 ml min^-1 kg^-1, respectively. Interestingly, the factorial aerobic scope was temperature-independent and remained at 7.0 which, at each T_b, was primarily the result of an increase in V_{b kg}, governed by approximate two-fold increases both in heart rate (f_H) and cardiac stroke volume (V_{S kg}). Both at 25°C and 36°C, the increase in V_{b kg} alone was not sufficient to provide all of the additional oxygen required to attain maximal VO_{2 kg}, as indicated by a decrease in the blood convection requirement (V_{b kg} / VO_{2 kg}), hence there was a compensatory two-fold increase in (C_aO₂ - C_vO₂). Although associated with an increase in haemoglobin-oxygen affinity, a decrease in T_b did not impair unloading of oxygen at the tissues and act to reduce (C_aO₂ - C_vO₂); both C_aO₂ and C_vO₂ were maintained across T_b. The change in VO_{2 kg} with T_b, therefore, is solely reliant on the thermal dependence of V_{b kg}. Maintaining a high factorial aerobic scope across a range of T_b confers an advantage in that cooler animals can achieve higher absolute aerobic scopes and presumably improved aerobic performance than would otherwise be achievable.