Trim the escarole and discard any tough or bruised leaves. Trim off the root end. Cut the head of escarole into quarters. Rinse well. Shake escarole to remove any excess moisture.
Heat the oil in a large saucepan and add the garlic. Let it cook briefly, then add the escarole. Do not add any water except that which clings to the leaves. Cover and cook for ten to fifteen minutes, stirring occasionally so that the cooking will be even.
Sprinkle with salt and pepper. Serve with olive oil and vinegar, if desired. Sautéed escarole may also be served cold with oil and vinegar.