Oxygen is an important factor for the quality of wine aged in barrels. The development of a tool to classify wood by its oxygen transmission rate (OTR) has made it possible to use the same batch of wood to make barrels that oxygenate twice as much as others. Therefore, the aim of this study was to evaluate the phenolic composition and colour of the same red wine aged for twelve months in barrels with a low oxygen transmission rate (LOTR) and with a high oxygen transmission rate (HOTR). The results showed that the same wine evolves differently in barrels with different oxygenation rates. Wines that received lower oxygenation (LOTR) had a higher polymeric pigment and total phenol content that were more polymerized. In these wines, the release of low molecular weight wood compounds was faster and higher than in the case of those aged in HOTR barrels. However, the wines from HOTR barrels maintained a higher level of anthocyanins and a more tannic character. Wines aged in LOTR barrels showed a higher colour intensity due to the increased formation of new pigments. These wines will maintain their red colour better than those aged in HOTR barrels.