Originally Posted by Frequent flyer 101

You'll get to a point where you can enter frequent flyer numbers for each passenger. Just select BA from the drop down and enter your Executive Club numbers. If you can't do it during booking, you can always go to the QR website and manage your booking (you need booking code and surname). You can then edit the passenger info. One of the options is frequent flyer number. It's generally quite straightforward to do.