Reid was adjudged to have fouled Ramires in the box and Eden Hazard dispatched the resulting spot-kick to ensure Jose Mourinho's unbeaten Premier League record at home continues.
However, Reid believes the Brazilian went to ground very easily and is disappointed to leave Stamford Bridge without all three points.
"For me, it was very soft. There was obviously contact there but it was a fair shoulder-to-shoulder challenge and Ramires has gone to ground very easily," he said.
"Going into the dying seconds of the game leading 2-1 and to then concede a penalty - we all feel very hard done by."
After trailing 1-0 at half-time through Samuel Eto'o's goal, Steve Clarke's side improved considerably and deservedly led through a Shane Long header and a Stephane Sessegnon scuffed effort, with Petr Cech at fault having failed to smother the Benin international's attempt.
The Baggies had opportunities to wrap up the result and Reid was left rueing their missed chances after Hazard's dramatic equaliser.
"Second half we came out with a little bit more confidence and belief," he said. "We had some great chances and could have put the game to bed in the last 15 minutes.
"It's always heartbreaking conceding a penalty that late in the game, especially at Stamford Bridge.
"Their home record under Jose Mourinho is top class and to break that would have been something special. At the moment, it feels like a defeat."