Oldham earned an FA Cup third round trip to Liverpool on 7 January after Chris Taylor's second-half strike proved enough to beat Southend.
Neil Harris and Bilel Mohsni forced fingertip saves from Latics goalkeeper Alex Cisak inside the first 18 minutes.
But Southend were down to 10 men on 38 minutes when Mohsni was sent off for fouls on Kieran Lee and Dean Furman.
James Wesolowski's lay-off then set up Taylor to smash home from 10 yards for the only goal just before the hour.
Oldham's trip to Anfield, where they have not won since 1913, will be their first meeting with Liverpool in 17 years - since their Premiership days.
Oldham manager Paul Dickov told BBC Radio Manchester:
"I'm very proud for lots of reasons. For my staff, for my chairman, for the directors, for the players and everyone who works at the football club.
"For us, at the start of the season, to get to the third round and hopefully draw a Premier League club was like our cup final.
"It's fitting that someone who supports the club, somebody who loves the place, scored the goal that gets us there."
Southend United manager Paul Sturrock told BBC Essex:
"I've let everybody down. I know there's a footballer in there [Bilel Mohsni], but too many times he's let us down.
"It's cost us a lot of money. I pick the team and I made a decision to play him and it's shot us in the foot.
"I should have probably taken him off. He just looked as if he was a walking foul again."
Live Text Commentary
Full Time The referee brings the game to a close.90:00 +2:52
The ball is crossed by Chris Taylor, blocked by Michael Timlin.90:00 +1:39
Anthony Grant challenges Josh Parker unfairly and gives away a free kick. The free kick is swung in right-footed by Chris Taylor.90:00 +0:22
Corner taken by Chris Taylor from the left by-line.89:05
The ball is crossed by Sean Clohessy.87:34
The ball is sent over by Filipe Morais.85:28
Blair Sturrock fouled by Dean Furman, the ref awards a free kick. The free kick is delivered left-footed by Ryan Hall from left channel, clearance by Josh Parker.82:44
Corner taken left-footed by Kane Ferdinand from the right by-line, Alex Cisak makes a save.81:41
Unfair challenge on Blair Sturrock by Chris Taylor results in a free kick. Free kick taken by Sean Clohessy.79:53 Substitution
Substitution (Oldham) makes a substitution, with Filipe Morais coming on for Luca Scapuzzi.78:53 Substitution
Substitution Josh Parker joins the action as a substitute, replacing Tom Adeyemi.77:47
Tom Adeyemi takes a shot. Save made by Luke Daniels.75:15
The ball is delivered by Kieran Lee.74:51
Chris Taylor takes a shot. Blocked by Luke Prosser.73:58
Blair Sturrock concedes a free kick for a foul on Zander Diamond. Dean Furman restarts play with the free kick.72:20
Kane Ferdinand takes the inswinging corner, clearance made by Nathan Clarke. Inswinging corner taken by Ryan Hall from the right by-line played to the near post, Dean Furman manages to make a clearance.71:09 Substitution
Substitution Kane Ferdinand is brought on as a substitute for Neil Harris.70:10
A cross is delivered by Paul Black, clearance by Luke Prosser.69:09
Unfair challenge on Dean Furman by Blair Sturrock results in a free kick. Direct free kick taken by Zander Diamond.68:41 Substitution
Substitution Ryan Leonard leaves the field to be replaced by Ryan Hall.
Blair Sturrock concedes a free kick for a foul on James Wesolowski. Paul Black restarts play with the free kick.64:39
Neil Harris is flagged offside by the assistant referee. Indirect free kick taken by Alex Cisak.62:15
Luke Daniels takes the free kick.62:15 Substitution
Substitution Luke Prosser comes on in place of Chris Barker.62:15
Corner taken by Chris Taylor from the left by-line to the near post, Zander Diamond produces a header from close range which bounces off the post. Zander Diamond handles the ball and concedes a free kick.61:51
Chris Taylor takes a shot. Mark Phillips gets a block in.61:27
Tom Adeyemi delivers the ball, save by Luke Daniels.59:47
Neil Harris delivers the ball, Alex Cisak makes a save.59:16
Effort from the edge of the area by Shefki Kuqi goes wide of the left-hand upright.57:30
The assist for the goal came from James Wesolowski.57:30 Goal scored
Goal! - Chris Taylor - Oldham 1 - 0 Southend Chris Taylor scores a goal from inside the penalty area to the top left corner of the goal. Oldham 1-0 Southend.52:41
Free kick awarded for an unfair challenge on Paul Black by Ryan Leonard. Alex Cisak takes the free kick.52:14
Chris Taylor handles the ball and concedes a free kick. Luke Daniels takes the indirect free kick.51:28
Shefki Kuqi takes a shot. Neil Harris gets a block in. Tom Adeyemi concedes a free kick for a foul on Anthony Grant. Direct free kick taken by Luke Daniels.50:37
The ball is crossed by Tom Adeyemi, blocked by Neil Harris. Corner from right by-line taken by Chris Taylor.48:55
Shot from just outside the box by Dean Furman goes over the bar.46:15
Chris Taylor takes a shot. Save by Luke Daniels. The referee blows for offside against Kieran Lee. Free kick taken by Luke Daniels.45:54
A cross is delivered by Sean Clohessy, Nathan Clarke makes a clearance.45:01
The second half has started.45:00 +2:24 Half time
Half Time The referee blows for half time.45:00 +1:27
Tom Adeyemi challenges Michael Timlin unfairly and gives away a free kick. Mark Phillips restarts play with the free kick. A cross is delivered by Michael Timlin.45:00 +0:43
Zander Diamond challenges Blair Sturrock unfairly and gives away a free kick. Free kick crossed left-footed by Peter Gilbert, clearance made by Nathan Clarke.44:35
Corner taken by Peter Gilbert from the left by-line played to the near post, Effort on goal by Blair Sturrock from inside the penalty area goes harmlessly over the bar.41:59
Blair Sturrock takes a shot from just inside the penalty box which clears the bar.40:48
The ball is swung over by Michael Timlin, Alex Cisak makes a save.40:30
Unfair challenge on Sean Clohessy by Chris Taylor results in a free kick. Direct free kick taken by Michael Timlin.38:36
Centre by Paul Black, Michael Timlin makes a clearance. Inswinging corner taken right-footed by Chris Taylor.37:42
Free kick crossed by Chris Taylor.37:42 Dismissal
Dismissal Bilel Mohsni is sent off by the referee for second bookable offence.37:22
Foul by Bilel Mohsni on Dean Furman, free kick awarded.36:59
Ryan Leonard challenges Luca Scapuzzi unfairly and gives away a free kick. Paul Black restarts play with the free kick.35:58
Free kick awarded for a foul by Blair Sturrock on Zander Diamond. Alex Cisak takes the direct free kick.34:41
Kieran Lee sends in a cross.33:47
Ryan Leonard takes a shot. Alex Cisak makes a comfortable save.33:32
Luca Scapuzzi takes a shot. Save by Luke Daniels.32:16
Tom Adeyemi takes a shot from just outside the penalty area which clears the crossbar.31:46
Michael Timlin challenges Shefki Kuqi unfairly and gives away a free kick. Alex Cisak restarts play with the free kick.30:58
Michael Timlin takes a shot. Save by Alex Cisak. Chris Barker takes a inswinging corner from the right by-line played to the near post.30:27
Dean Furman takes a shot. Save made by Sean Clohessy.29:20
Shefki Kuqi delivers the ball.25:58
Nathan Clarke takes the free kick.25:58 Booking
Booking Caution for James Wesolowski.25:29 Booking
Booking Anthony Grant booked.25:07
Unfair challenge on Shefki Kuqi by Anthony Grant results in a free kick.24:39
Tom Adeyemi takes a shot. Blocked by Chris Barker.23:41
Free kick awarded for an unfair challenge on Anthony Grant by Luca Scapuzzi. Free kick crossed by Michael Timlin.22:18
Unfair challenge on Shefki Kuqi by Mark Phillips results in a free kick. The ball is sent over by Chris Taylor, Headed effort from deep inside the penalty area by Zander Diamond misses to the right of the target.21:31
Alex Cisak takes the free kick.21:31 Booking
Booking The referee shows Bilel Mohsni a yellow card for unsporting behaviour.21:05
Foul by Bilel Mohsni on Kieran Lee, free kick awarded.19:55
Foul by Bilel Mohsni on Dean Furman, free kick awarded. Alex Cisak takes the free kick.19:45
Neil Harris sends in a cross, clearance by Nathan Clarke.19:12
James Wesolowski challenges Anthony Grant unfairly and gives away a free kick. Direct free kick taken by Chris Barker.17:24
Neil Harris takes a shot. Save made by Alex Cisak. Corner taken left-footed by Peter Gilbert from the right by-line, Close range header by Mark Phillips goes over the crossbar.15:05
Bilel Mohsni takes a shot. Alex Cisak makes a save. Corner taken by Peter Gilbert played to the near post.13:26
Tom Adeyemi sends in a cross, Anthony Grant manages to make a clearance.12:14
James Wesolowski concedes a free kick for a foul on Anthony Grant. Free kick taken by Chris Barker.9:38
The ball is swung over by Dean Furman, Luke Daniels manages to make a clearance.8:33
Free kick awarded for a foul by Blair Sturrock on Paul Black. Paul Black restarts play with the free kick.5:45
Peter Gilbert gives away a free kick for an unfair challenge on Tom Adeyemi. Free kick taken by Chris Taylor. Centre by Kieran Lee, Blair Sturrock gets a block in.4:19
The ball is sent over by Tom Adeyemi, blocked by Michael Timlin.3:42
Unfair challenge on Shefki Kuqi by Chris Barker results in a free kick. Nathan Clarke takes the direct free kick.2:54
Bilel Mohsni takes a shot. Save by Alex Cisak.0:00
The ref blows the whistle to start the match.
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