Gabriel Tamas fired home four minutes from time to snatch a hard-earned point at the Madejski Stadium and nudge West Bromwich Albion closer to a quick return to the Barclays Premier League.
Tamas' late equaliser took the Baggies nine points clear of nearest challengers Nottingham Forest, who did not play, and within a point of leaders Newcastle who have two games in hand.
Albion looked like being on the receiving end of Reading's recent revival when Gylfi Sigurdsson opened the scoring in the sixth minute. Scott Carson made a fine save to deny Jimmy Kebbe as the visitors hung on.
Cardiff were the biggest winners on a day when their fellow play-off hopefuls slipped up and allowed Ian Holloway's Blackpool to close the gap on the top six to just four points.
Dave Jones' men edged past relegation-haunted Crystal Palace in the early kick-off at Selhurst Park, where Gabor Gyepes' early strike was cancelled out by Clint Hill before Chris Burke hit a 67th-minute winner.
The win sent Cardiff jumping to fourth while things look bleak for Palace who now stand four points from safety having been crippled by their 10-point deduction for going into administration earlier in the season.
Leicester blew their big chance to cement fourth after sliding to a farcical 1-0 defeat at east Midlands rivals Derby. Andy King's soft 19th-minute back-pass was completely missed by Foxes keeper Chris Weale who let it trickle under his foot.
Meanwhile, Swansea were held to a goalless draw by Roy Keane's improving Ipswich, Blackpool beat Plymouth 2-0, Doncaster edged a nervous south Yorkshire derby at Barnsley and Leroy Lita salvaged a point for Middlesbrough against Watford at Vicarage Road.
Elsewhere, Sheffield Wednesday held on for a 1-1 draw at Coventry, doomed Peterborough crashed to their 24th defeat of the season as Bristol City's David Clarkson scored the only goal at London Road, while a late comeback from Queen's Park Rangers earned them a point in a 2-2 draw at Preston.
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