Cut corn kernels from ears, discarding cobs. Heat oil in a large heavy skillet over moderately high heat until hot but not smoking, then saute corn and season, to taste, stirring, until tender, about 4 minutes.
Add garlic and saute, stirring, 1 minute. Add vinegar and cook, stirring, until most is evaporated, about 1 minute. Add tomatoes and cook, gently stirring, 1 minute.
Remove skillet from heat and stir in scallions. Transfer vegetables to a large plate to cool and season with salt and pepper.