Saints have not won a match since winning at Reading in November
Reading striker Shane Long headed an equaliser to keep his side second in the Championship table and push Southampton into the bottom three.
David McGoldrick, who had hit the bar in the first half, put Saints ahead on 74 minutes when he slotted home a pass from lively substitute Kayne McLaggon.
But Long levelled 10 minutes later with a header from Stephen Hunt's free-kick.
Kevin Doyle hit the bar with a header and the Saints had a strong penalty appeal rejected in a thrilling finish.
Southampton manager Jan Poortvleit:
"I have got nothing but good words to say about how they came into the game and the way we matched Reading, who are a very good side.
"They have all done a really good job but I just wish we could have picked up all three points rather than just one.
"Hopefully, we can go on and win more games to get out of the relegation zone because we're better than that."
Reading manager Steve Coppell:
"At the end of the season this may prove an excellent point. We showed fortitude, determination and resilience to get back into it.
"It is not fortuitous that we win or draw games when we've gone behind in the last 10 minutes.
"We showed a huge amount of desire to get back into the game - I'm delighted with the way we approached it."
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