Richard Langley turned from hero to zero as QPR earned a draw in this tense and physical play-off semi-final at Boundary Park.
The QPR midfielder scored his teams precious equaliser only to be sent off for two bookable offences in the 80th minute.
First, Langley was cautioned for diving in to a challenge with Darren Sheridan. Within 60 seconds, he caught David Eyres in an off the ball incident and will now miss the second leg at Loftus Road on Wednesday.
Langley was blasted by his manager Ian Holloway, who said: "Richard has let us down.
"I was going to take him off anyway because I thought he was losing his head. What he did was petulant and I'm not at all happy with him.
"You can't keep blaming referees and the fact we had so many people booked was down to a lack of professionalism.
"We need to keep our heads much better on Wednesday. It was summed up at the end when Richard Pacquette kicked the ball away and got an Oldham free-kick moved to the edge of the box - they could have scored from that." Oldham manager Iain Dowie, who was up against the club he lead briefly on a caretaker basis two years ago, said the tie was very much in the melting pot.
He said: "It's going to be a great atmosphere and a very tough game for us so it is vital the lads keep their focus.
"This was an edgy occasion, but we created the better chances and I am a bit disappointed that we didn't finish the game with a victory to take down there." There were few chances in the first half, with the best falling to QPR's Paul Furlong who headed over after just three minutes.
The visitors were on top but things changed after veteran Eyres fired Oldham ahead just before the half hour.
Eyres hit his 16th of the season with a 20-yard free-kick which took a deflection off the defensive wall.
Oldham took control only to concede within two minutes of the restart as Tommy Williams crossed to the far post and Langley slid in for a close-range finish.
The rest of the chances fell to Oldham but Paul Murray fired over and Josh Low had his shot blocked.
Rangers suffered an injury blow in the second half when Matthew Rose was carried off after an innocuous tackle.