Long moved from the Royals to Albion 18 months ago after scoring 54 goals in 203 appearances in all competitions.
The Republic of Ireland international is battling with Romelu Lukaku to start but will show respect if he finds the net against Brian McDermott's side.
Long said: "I have nothing but respect for Reading, the supporters and everybody involved there.
"It will be strange to go back and play against them and be in the away dressing room.
"It would also be strange to score against Reading and, if I scored a hat-trick, I wouldn't celebrate any of the goals."
- Sports & Recreation