Originally Posted by ISTFlyer

I have used both the BA and TK Lounges at IAD in the near past.
Just to let you know that, the TK Lounge usually is super crowded during QR flight times and it might be difficult to find a seat. Although the food over there is quite decent even though it's not at pre-COVID levels.

The BA Lounge has the pre-flight Club dining section closed and everyone is seated at the main area ( not sure if there is a private arrangement for F pax and GGL's ) thus if there is a BA flight that would depart at the same time as your flight, you might also have difficulty finding seats over there and the BA Lounge only opens during BA flight times thus if you are leaving with the morning QR flight out of IAD, the BA Lounge would not be open at that time.