Author summary Why was this study done? Reducing the portion size of food reduces the amount of food people eat. Reducing the size of servings of alcoholic drinks sold by the glass in licensed premises could reduce alcohol consumption but there is no real-world evidence for this. What did the researchers do and find? We asked 21 licensed premises in England to remove the offer of their larger serving size of wine by the glass (usually 250 ml) from available options for 4 weeks. We compared the total daily volume of wine sold during the intervention period to that sold during nonintervention periods. Removing the largest serving size of wine by the glass (usually 250 ml) in licensed premises reduced the volume of wine sold by 7.6%. There was no evidence that it impacted sales of beer or cider, or total daily revenues. What do these findings mean? This intervention merits consideration for inclusion in alcohol licensing regulations. These findings are limited by our inability to assess the sales of cocktails and spirits and the potential for people to have compensated for reducing wine consumption by drinking more cocktails and spirits.