BA is now offering the chance to pick your premium cabin meal 30 days before your flight. On the BA web site if you look up your booking in “Manage My Booking” and scroll right to the very bottom you see the Service requests menu above.
If the Order your in-flight meal link is available you can pick your meal.
I’m travelling on BA next month to JFK from Heathrow in First and these are the offerings:
As it’s Thanksgiving in the US I have picked the traditional turkey. Plus, I don’t eat fish!
If you need a special dietary meal, pick the Special Meal tab and you select a special religious or dietary meal from there.
Some flights don’t offer the pre-order option, but if you want to make sure of your entree, it’s worth doing pre-booking in my view. If your flight doesn’t offer the pre-booking you can still book a dietary or religious meal.