The Reds dominated large periods and created the better chances, before Matt Day struck a stunning 25-yard thunderbolt with seconds remaining which beat keeper Ben Hamer at his near post.
The sickening defeat keeps Crawley entrenched in the relegation zone following one win from their last seven games. However, United, who remain unbeaten at the top, could have been ahead as early as the eighth minute.
Striker Marvin Robinson had a free header from an Andy Burgess cross and was denied by a stunning point-blank stop by Hamer.
The let-off sparked the home side into life and they went close after 17 minutes through defender Pat Sappleton, who was making his first start of the season. The big defender almost caught out Billy Turley with a chip from 20 yards but the visiting keeper scrambled back to tip over the bar.
Hollins' side went close again a minute later when a cross from Tony Scully found striker Jake Edwards five yards from goal. The big target man, usually deadly in the air, somehow failed to get a connection on his header and Chris Willmott was able to punt clear.
Edwards almost made amends moments later with a header following more good work by Scully, but this time he did not get enough power on his effort, giving Turley a comfortable save.
Crawley were given a warning of the threat Jim Smith's title favourites posed on 23 minutes when Day nodded inches over from a cross by Carl Pettefer. The hosts were soon back in control, however, and Turley had to be alert on 35 minutes to make a low save from Dannie Bulman's pile driver from outside the box.
The Reds' best chance of the first half came four minutes later when Bulman laid the ball off neatly for Lee Blackburn to fire just wide from the edge of the area.
Sappleton justified his selection ahead of former Oxford defender Dave Woozley just before half-time with two brilliant goal-saving interventions.
He first cleared off the line from Wlilmott's towering header following a corner. Then he made a brave last-ditch sliding tackle to deny Robinson a shot from close range.
Crawley continued to dominate after the break and almost went ahead within 60 seconds of the restart. Michael Bostwick tried an audacious 35-yard shot which sped just past the post.
Scully also went close from long range on the hour with an angled volley from the edge of the area, before Edwards left the home crowd gasping again with a similar effort three minutes later.
Blackburn tested Turley with another drive from 20 yards and then, two minutes later, Bostwick came within fractions of scoring with a second audacious effort.
Crawley were almost punished for their wastefulness on 78 minutes when Oxford hit the woodwork twice in quick succession.
Hamer pushed a header from Burgess on to his crossbar following a long ball by Day. The rebound fell kindly for substitute Yemi Odubade, but the pacy striker could only nod the ball back against the bar.
It proved only a reprieve for unlucky Reds as Day won the game in the dying seconds. There appeared no danger when he picked the ball up 30 yards from goal, before he unleashed a shot that skidded along the wet turf before finding the bottom corner.
The sickening defeat keeps Crawley entrenched in the relegation zone following one win from their last seven games. However, United, who remain unbeaten at the top, could have been ahead as early as the eighth minute.
Striker Marvin Robinson had a free header from an Andy Burgess cross and was denied by a stunning point-blank stop by Hamer.
The let-off sparked the home side into life and they went close after 17 minutes through defender Pat Sappleton, who was making his first start of the season. The big defender almost caught out Billy Turley with a chip from 20 yards but the visiting keeper scrambled back to tip over the bar.
Hollins' side went close again a minute later when a cross from Tony Scully found striker Jake Edwards five yards from goal. The big target man, usually deadly in the air, somehow failed to get a connection on his header and Chris Willmott was able to punt clear.
Edwards almost made amends moments later with a header following more good work by Scully, but this time he did not get enough power on his effort, giving Turley a comfortable save.
Crawley were given a warning of the threat Jim Smith's title favourites posed on 23 minutes when Day nodded inches over from a cross by Carl Pettefer. The hosts were soon back in control, however, and Turley had to be alert on 35 minutes to make a low save from Dannie Bulman's pile driver from outside the box.
The Reds' best chance of the first half came four minutes later when Bulman laid the ball off neatly for Lee Blackburn to fire just wide from the edge of the area.
Sappleton justified his selection ahead of former Oxford defender Dave Woozley just before half-time with two brilliant goal-saving interventions.
He first cleared off the line from Wlilmott's towering header following a corner. Then he made a brave last-ditch sliding tackle to deny Robinson a shot from close range.
Crawley continued to dominate after the break and almost went ahead within 60 seconds of the restart. Michael Bostwick tried an audacious 35-yard shot which sped just past the post.
Scully also went close from long range on the hour with an angled volley from the edge of the area, before Edwards left the home crowd gasping again with a similar effort three minutes later.
Blackburn tested Turley with another drive from 20 yards and then, two minutes later, Bostwick came within fractions of scoring with a second audacious effort.
Crawley were almost punished for their wastefulness on 78 minutes when Oxford hit the woodwork twice in quick succession.
Hamer pushed a header from Burgess on to his crossbar following a long ball by Day. The rebound fell kindly for substitute Yemi Odubade, but the pacy striker could only nod the ball back against the bar.
It proved only a reprieve for unlucky Reds as Day won the game in the dying seconds. There appeared no danger when he picked the ball up 30 yards from goal, before he unleashed a shot that skidded along the wet turf before finding the bottom corner.