Gamma oscillations are believed to arise from the interaction between excitation and inhibition (E-I) in the neural circuitry. However, the dependency of gamma power on E-I interaction is not well characterized. Increasing the drift-rate of the visual grating, which changes E-I balance, increases the peak frequency of gamma while power initially increases and later attenuates. Importantly, this power versus drift-rate tuning curve is altered for subjects with autism or premenstrual dysphoric disorder. A recent MEG study in humans (Orekhova et al., 2020) examined the combined effect of contrast and drift-rate on gamma power and found that the preferred temporal frequency reduced at higher contrasts (leftward shift of drift-rate versus gamma power curve), which they hypothesized was due to an excess of excitatory drive, leading to a stronger inhibition resulting in the attenuation of gamma power at high drift-rates. We tested this hypothesis in the macaque visual area V1 using a 48-channel microelectrode Utah array by varying either contrast or size of the grating that drifted at varying rates. Since increasing contrast changes both excitatory and inhibitory drives while increasing size mainly recruits surround suppression, we hypothesized that the two manipulations would shift the drift-rate tuning curve differently. Indeed, we observed a leftward shift with increasing contrast, as shown previously, and a rightward shift when the size was increased. Hence, gamma could reflect an optimal E-I balance. Understanding the dependence of gamma on such E-I manipulations holds promise for developing gamma-based biomarkers for diagnosing mental disorders due to E-I imbalance.