Oxygen has a fundamental role in the vinification process and occurs in the various stages, particularly during the fermentation and aging of wines. Phenolic compounds, such as oxygen, are relatively important in wine quality. Among polyphenols, anthocyanins and tannins are the most important compounds since they contribute to the organoleptic characteristics of wines, particularly colour and astringency. During wine-making and aging, phenolics extracted from grapes gradually change owing to biochemical reactions, which result in a decrease in astringency as well as colour stabilization. Therefore, addition of a measured amount of oxygen, referred to as a microoxygenation process, was proposed to improve wine quality by accelerating these transformations of phenols. In a microoxygenation process, it is assumed that modification of phenolic compound reactions by oxidation should result in more coloured and less astringent products. In this article, the role of oxygen, phenolics and microoxygenation application in wine technology has been reviewed.