Christian Fassnacht's last-minute strike saw Young Boys beat Rangers 2-1 in their Group G meeting in the Europa League.
The visitors opened the scoring a minute before the break thanks to Alfredo Morelos' 14th goal in just 13 starts this season, taking his overall tally for the club to a hugely impressive 62 strikes in just 109 games.
Young Boys: Ballmoos (6), Janko (6), Sorensen (6), Zesiger (6), Garcia (7), Fassnacht (6), Aebischer (6), Lustenberger (6), Gaudino (7), Assale (7), Nsame (7)
Subs: Ngamaleu (6), Lotomba (6)
Rangers: McGregor (6), Tavernier (4), Helander (6), Goldson (6), Barisic (7), Kamara (6), Arfield (6), Jack (6), Davis (6), Ojo (6), Morelos (8)
Subs: Stewart (6)
Man of the match: Alfredos Morelos
However, Gerrard's team were pegged back five minutes into the second half thanks to Roger Assale's close-range finish, before the Young Boys winger took advantage of James Tavernier's mistake to win it with the last kick of the match.
As a result, instead of topping the group, Rangers drop to third after Porto's defeat at Feyenoord.
How Young Boys stunned Rangers
In a first half low on quality and chances - perhaps because of the artificial pitch - it was the home team who spurned the best opening when in-form striker Jean-Pierre Nsame somehow managed to side-foot wide of a gaping goal from just three yards out after being found by Ulisses Garcia's clever header.
And Rangers made their opponents pay for that miss when taking the lead against the run of play on the cusp of half-time. There appeared little danger as Borna Barisic looked to pick out Morelos's run down the left channel.
That is until Young Boys defender Cedric Zesiger got too tight on the Colombian, who cleverly spun his man before advancing forward and keeping his cool to beat David Von Ballmoos with a neat finish at the near post.
The hosts soon found themselves back on level terms, though, after Tavernier carelessly lost possession in the right-back berth, allowing Garcia to cross for the unmarked Assale to tap in from close range.
Rangers made two changes with Filip Helander and Glen Kamara both named in the starting lineup. Greg Stewart, who scored his first Rangers goal in the 5-0 victory over Aberdeen last time out, dropped to the bench along with defender Nikola Katic.
However, with the clock ticking down and just 60 seconds left to play, the Swiss champions won it after the unfortunate Tavernier made a complete hash of his attempted clearance, giving Fassnacht a clear run on goal.
And from a tight angle, the Switzerland international beat Allan McGregor at his near post with a low drive to send most of the 26,000 crowd at the Stade de Suisse into delirium.
- Young Boys have ended Rangers' nine game unbeaten run on the road across all competitions (W7 D3 L0 previously), with this Rangers' first away defeat since May against Kilmarnock (2-1)
- Young Boys have won 13 of their previous 18 home matches in the Europa League (D1 L4), winning 2-1 in each of their last two contests after conceding the first goal
- Rangers are winless in their last 13 away matches in major European competition since beating Sporting CP 2-0 in the UEFA Cup in April 2008, drawing eight games and losing five times since
- Rangers are the first British side to lose to a 90th minute winner in the Europa League since Liverpool in April 2016 versus Villarreal
- Rangers forward Alfredo Morelos has scored 14 goals in his 18 appearances for Rangers in all competitions this season, netting nine goals in the Europa League group stages and qualifying combined
What the manager said...
Steven Gerrard: "We were a VAR away from taking a point from that match. We should have had a second yellow card for [Frederik] Sorensen, because he has booked Alfredo for exactly the same incident. I believe they should have gone down to 10 men.
"The 'keeper has pulled off a world-class save when we could have gone 2-1 up and the referee has missed a blatant penalty, so we are a VAR away from either winning the game and if not, drawing it.
"I am frustrated for the players, who have given a lot for the team, but we have gifted them two gifts, so we need to learn from this and cut out individual errors because we have lost two games this season from individual errors."
Man of the Match - Alfredo Morelos
The forward was at his mischievous best in Switzerland, keeping the Young Boys defenders on their toes throughout the 90 minutes.
The Colombia international did brilliantly to turn his man, before finishing expertly for his side's opener and on another night, he may have won a second-half penalty after a clash with Garcia.
And with nine goals to his name already in this competition, including qualifying, the frontman is once again proving why he is Rangers' most valuable player.
Rangers take on Hamilton at Ibrox in the Scottish Premiership on Sunday afternoon.