The non-league side trailed twice at Oakwell before coming away with a 3-3 draw.
They'll need to lean on that experience now as they look to just stay in the tie.
Post update
Grimsby v Slough Town (19:45 GMT)
Video content
Video caption: Slough player-manager Scott Davies scores sensational free-kick against GrimsbySlough player-manager Scott Davies scores sensational free-kick against Grimsby
Slough Town player-manager Scott Davies won't score many better goals than the firecracker free-kick that gave his side the lead against Grimsby in the first meeting of these sides.
In front of a record crowd at Arbour Park, the National League South side had been heading straight through until Danny Rose drew Grimsby level 15 minutes from full-time to earn the Mariners a replay at home.
Slough, who are currently 20th in the sixth tier and hovering above the drop zone, have reached the FA Cup second round four times previously, the most recent occasion being in 2018-19.
Grimsby, meanwhile, go into the match buoyed by a victory against Morecambe in the league at the weekend, ending a run of seven games without a win in all competitions.
GOAL: Horsham 0-1 Barnsley
Nicky Cadden (3 mins)
Not the start the non-league side wanted.
A deep cross to the back post catches home goalkeeper Lewis Carey out and he can only palm it straight to Nicky Cadden to tap home from about three yards out.
A tough task just got a lot tougher for the seventh-tier outfit.
Scarborough's second bite at second round
Forest Green v Scarborough Athletic (19:45 GMT)
Video content
Video caption: Highlights: Scarborough Athletic 1-1 Forest GreenHighlights: Scarborough Athletic 1-1 Forest Green
Teenager Olly Sully saved Forest Green's blushes and broke Scarborough hearts during the first meeting of these two sides.
The 18-year-old scored a 93rd-minute equaliser to force a 1-1 draw after Scarborough had taken a 27th-minute lead.
This is the Seadogs' first appearance in the FA Cup first round since they reformed in 2007, meaning a win and a place in the second round would make more history for the sixth-tier side who play in National League North.
The prize for whoever comes out on top is a trip to League One Blackpool.
KICK-OFF
Horsham 0-0 Barnsley
We're under way in our first FA Cup first-round replay of the night.
Can the seventh-tier side pull off an almighty shock?
Up for the Cup
Horsham v Barnsley (19:30 GMT)
PA MediaCopyright: PA Media
Horsham fans have been getting in early, ready for their club's big night in the FA Cup.
Rex FeaturesCopyright: Rex Features
It's commonplace for teams across the world to have a hardcore of vocal support known as the ultras.
You'd hope lard doesn't feature heavily in the diet of any of the players out on the pitch this evening.
Rex FeaturesCopyright: Rex Features
And it wouldn't be an FA Cup tie at a non-league ground without a young fan holding up a foil cut-out of the trophy.
Not a bad effort at all that.
Horsham hope to make most of record backing
Horsham v Barnsley (19:30 GMT)
Rex FeaturesCopyright: Rex Features
Horsham chairman Kevin Borrett is looking forward to welcoming a stadium-record crowd for tonight's game.
The Hornets moved into Camping World Community Stadium in 2019 and are looking to reach the second round for the first time since 2007-08, when they took Swansea to a replay.
"Tonight is just a great experience for the whole club and the town. We're expecting a record crowd," he told BBC Radio 5 Live.
"With the town behind us we're going to give it our all. We're a self-sustaining club and we live within our means."
Tuesday's FA Cup first-round replays
Kick-off at 19:45 GMT unless stated
Horsham v Barnsley (19:30 GMT)
Accrington Stanley v Doncaster Rovers
Burton Albion v Port Vale
Derby County v Crewe Alexandra
Forest Green Rovers v Scarborough Athletic
Grimsby Town v Slough Town
Salford City v Peterborough United
York City v Chester
A time for heroes?
Horsham v Barnsley (19:30 GMT)
Video content
Video caption: Highlights: Barnsley 3-3 HorshamHighlights: Barnsley 3-3 Horsham
Seventh-tier Horsham pulled off one of the most famous results of their 142-year history with a 3-3 draw at League One Barnsley in their FA Cup first round tie 10 days ago.
The two teams will shortly do it all over again, with the non-league side looking to reach the second round for the second time ever.
We've got that, plus all the action from seven other first-round replays.
Live Reporting
Ian Woodcock, Sophie Hurcom and Alex Seftel
All times stated are UK
Post update
Horsham 0-1 Barnsley
The non-league side trailed twice at Oakwell before coming away with a 3-3 draw.
They'll need to lean on that experience now as they look to just stay in the tie.
Post update
Grimsby v Slough Town (19:45 GMT)
Video content
Slough Town player-manager Scott Davies won't score many better goals than the firecracker free-kick that gave his side the lead against Grimsby in the first meeting of these sides.
In front of a record crowd at Arbour Park, the National League South side had been heading straight through until Danny Rose drew Grimsby level 15 minutes from full-time to earn the Mariners a replay at home.
Slough, who are currently 20th in the sixth tier and hovering above the drop zone, have reached the FA Cup second round four times previously, the most recent occasion being in 2018-19.
Grimsby, meanwhile, go into the match buoyed by a victory against Morecambe in the league at the weekend, ending a run of seven games without a win in all competitions.
GOAL: Horsham 0-1 Barnsley
Nicky Cadden (3 mins)
Not the start the non-league side wanted.
A deep cross to the back post catches home goalkeeper Lewis Carey out and he can only palm it straight to Nicky Cadden to tap home from about three yards out.
A tough task just got a lot tougher for the seventh-tier outfit.
Scarborough's second bite at second round
Forest Green v Scarborough Athletic (19:45 GMT)
Video content
Teenager Olly Sully saved Forest Green's blushes and broke Scarborough hearts during the first meeting of these two sides.
The 18-year-old scored a 93rd-minute equaliser to force a 1-1 draw after Scarborough had taken a 27th-minute lead.
This is the Seadogs' first appearance in the FA Cup first round since they reformed in 2007, meaning a win and a place in the second round would make more history for the sixth-tier side who play in National League North.
The prize for whoever comes out on top is a trip to League One Blackpool.
KICK-OFF
Horsham 0-0 Barnsley
We're under way in our first FA Cup first-round replay of the night.
Can the seventh-tier side pull off an almighty shock?
Up for the Cup
Horsham v Barnsley (19:30 GMT)
Horsham fans have been getting in early, ready for their club's big night in the FA Cup.
It's commonplace for teams across the world to have a hardcore of vocal support known as the ultras.
Horsham are no different, well, except theirs are known as the Lardy Army. So-called, and I am genuinely not making this up, because they used to send a bar of lard to opposition clubs to let them know they would be coming.
You'd hope lard doesn't feature heavily in the diet of any of the players out on the pitch this evening.
And it wouldn't be an FA Cup tie at a non-league ground without a young fan holding up a foil cut-out of the trophy.
Not a bad effort at all that.
Horsham hope to make most of record backing
Horsham v Barnsley (19:30 GMT)
Horsham chairman Kevin Borrett is looking forward to welcoming a stadium-record crowd for tonight's game.
The Hornets moved into Camping World Community Stadium in 2019 and are looking to reach the second round for the first time since 2007-08, when they took Swansea to a replay.
"Tonight is just a great experience for the whole club and the town. We're expecting a record crowd," he told BBC Radio 5 Live.
"With the town behind us we're going to give it our all. We're a self-sustaining club and we live within our means."
Tuesday's FA Cup first-round replays
Kick-off at 19:45 GMT unless stated
A time for heroes?
Horsham v Barnsley (19:30 GMT)
Video content
Seventh-tier Horsham pulled off one of the most famous results of their 142-year history with a 3-3 draw at League One Barnsley in their FA Cup first round tie 10 days ago.
The two teams will shortly do it all over again, with the non-league side looking to reach the second round for the second time ever.
We've got that, plus all the action from seven other first-round replays.
Time for some giant-killing?