Anomalous phantom visual perceptions coupled to an aversion to some visual patterns has been associated with aberrant cortical hyperexcitability in migraine patients. Previous literature has found fluctuations of alpha oscillation (8-14 Hz) over the visual cortex to be associated with the gating of the visual stream. In the current study, we examined whether alpha activity was differentially modulated in migraineurs in anticipation of an upcoming stimulus as well as post-stimulus periods. We used EEG to examine the brain activity in a group of 28 migraineurs (17 with aura/11 without) and 29 non-migraineurs and compared the modulations of alpha power in the pre/post-stimulus period relative to onset of stripped gratings of 3 spatial frequencies 0.5, 3, and 13 cycles per degree (cpd). Overall, we found that that migraineurs had significantly less alpha power prior to the onset of the stimulus relative to controls. Moreover, relative to the control group, migraineurs had significantly greater post-stimulus alpha suppression (i.e event-related desynchronization) induced by the 3 cpd grating at the 2nd half of the experiment, the stimulus most often reported to induce visual disturbances. These findings taken together provide strong support of the presence of elevated cortical excitability in the visual cortex of migraine sufferers. We speculate that cortical hyperexcitation could be the consequence of impaired perceptual learning driven by the dysfunction of GABAergic inhibitory mechanism.