Honours were even at Boundary Park as two sides in the thick of the promotion battle fought out an entertaining game.
The Foxes were on course to seal their fifth win in six away games after Steve Howard fired them ahead, but Oldham hit back with a superb goal by midfield man Danny Whitaker.
Neil Harris' second-half double on top of David Martin's first-half equaliser saw Millwall complete an emphatic comeback against Leeds United at the New Den.
His intricate flick from Marc Laird's cross after 58 minutes buried a Leeds side who had stolen the lead through Luciano Becchio's first-half wonder strike.
The Argentinian scored a beauty from 22 yards with Leeds' first attempt at goal just after the half-hour when his left-foot arrow beat David Forde and nestled in the far corner.
Harris was also instrumental in Martin's 36th-minute equaliser for the dominant hosts, when the winger latched onto his reverse pass before lifting it over the advancing David Lucas.
Then Harris' delicate header guided Laird's right-foot cross into the far corner to give the Lions the lead before he made the game safe.
Southend United climbed into the final play-off spot as piled more misery on Swindon Town with a 2-1 win at Roots Hall thanks to goals from Alex Revell and Francis Laurent.
MK Dons dropped out of the top six following their 2-2 draw at Crewe Alexandra.
Luke Chadwick's 78th equaliser denied Crewe a much-needed victory as their coach, Steve Holland, came under fire from fans. After Sam Baldock fired the Dons into a 15th minute lead some of the home faithful unfurled a banner calling for Holland to go.
But his side fought back strongly before the interval, to lead through a Sean O'Hanlon own goal and a Shaun Miller strike.
A Danny Graham double was not enough for Carlisle United as Peterborough United snatched a point with a last gasp equaliser from Craig Mackail-Smith in a thriller at Brunton Park.
With 94 minutes on the clock the energetic Mackail-Smith ghosted between two defenders to latch onto a lofted through-ball and scuff his shot under Carlisle keeper Ben Alnwick.
Clive Platt snatched a winner for Colchester United and new manager Paul Lambert with just three minutes left on the clock at Stockport County.
Platt latched onto David Perkins' flick before lashing home from an angle. Perkins had put the Us ahead, with Matty McNeil levelling for the Hatters.
Hartlepool United staged a second-half fightback to register their first win in six games against a disappointing Walsall side.
It had looked as though the Saddlers were on their way to an easy victory when they went two goals ahead after only 13 minutes - through Michael Ricketts and Jabo Ibehre - and dominated for most of the first half.
But Danny Wilson's men turned it round in a frenetic second half and with Walsall failing badly the northern side ran out deserved winners.
Wilson made some decisive substitutions in the 64th minute bringing on Matty Robson and David Foley.
It took only eight minutes for Robson to make his mark, cutting through down the left and crossing for Antony Sweeney to reduce the arrears with a low shot.
Four minutes later Robson equalised with a cracking drive from 25 yards and Walsall were further punished in the 84th minute when the impressive Sweeney crossed and James Brown scored the winner with a superb header.
Goals from Danny Jackman, Ade Akinfenwa and Jason Crowe gave Northampton Town a comfortable 3-0 victory over Yeovil Town at Huish Park.
Chris Shuker scored after 39 minutes to give Tranmere Rovers their third away win of the season and condemned Leyton Orient to five defeats in their last six league games.
Rickie Lambert grabbed his tenth goal of the season as Bristol Rovers drew 1-1 at Huddersfield Town, Michael Flynn had given the Yorkshire side an early lead.
Brighton and Hove Albion and Hereford United played out a goalless draw at the Withdean Stadium.