Teddy Teuma and Dante Vanzeir were on the scoresheet for the Belgian outfit, who will be looking to protect their advantage when they make the trip to Glasgow.
Match preview
Following the first-leg defeat last week, Rangers boss Giovanni van Bronckhorst admitted that his side were fortunate to only lose by two goals, with the hosts dominating the contest for long spells.
The Gers will enter this match off the back of a positive result, though, having recorded a 2-0 victory over Kilmarnock in the Scottish Premiership on Saturday, which moved them onto six points from two matches.
Rangers finished second in the Scottish Premiership last season, four points behind the champions Celtic, while they lost to Malmo in the third qualifying round of the 2021-22 Champions League.
The Scottish club's last appearance in the group stage of the European Cup came back in 2010-11, but they were close to securing an automatic spot in this season's group stage, making it all the way to the final of the 2021-22 Europa League before losing on penalties to Eintracht Frankfurt.
Rangers are capable of putting in special performances in front of their own supporters, and the stadium will need to be bouncing on Tuesday night if the team are to stand any chance of navigating their way past an impressive Union SG outfit.
Union SG were only promoted back to the top flight of Belgian football in March 2021, with the team returning to the top tier for the first time in 48 years.
Incredibly, Karel Geraerts's side managed to finish top of Belgian First Division A last term, becoming the first side in Belgian history to manage that feat after earning promotion the previous campaign, while they ultimately finished second behind Club Brugge in the champions playoff to secure their spot at this stage.
Like Rangers, Union SG have already started their domestic league campaign, picking up four points from their opening three matches to sit in 10th position in the table.
Despite the impressive result in the first leg, Geraerts's side will enter this match off the back of a 3-0 defeat to Mechelen in the league on Saturday, and the same scoreline on Tuesday would see them eliminated from the Champions League in the third qualifying round.
Union SG are the third-most successful team in terms of top-tier Belgian championships, claiming 11, putting them behind Anderlecht (34) and Club Brugge (18), but it would be a special achievement if they managed to progress to the playoff round and then into the group stage of the Champions League.
Rangers Champions League form:
Rangers form (all competitions):
Union SG Champions League form:
Union SG form (all competitions):
Team News
Alfredo Morelos made a scoring return off the bench against Kilmarnock on Saturday in a huge boost for Rangers ahead of this European contest.
Gers boss Van Bronckhorst will be tempted to start the striker, but it appears more likely that he will again be named on the bench, with Antonio Colak, who also scored on Saturday, leading the line.
There are not expected to be any major surprises in the home side's XI on Tuesday, with Glen Kamara and Ryan Jack both set to come into the side, having been named on the bench against Kilmarnock in the league.
As for Union SG, head coach Geraerts shuffled his pack for the league match with Mechelen on Saturday, which ended in a 3-0 defeat for the champions.
All of the team's key players are expected to be fit for Tuesday's contest, with the same XI that started the first leg expected to take to the field for the first whistle at Ibrox.
Ross Sykes was among those left out of the starting side on Saturday, but the Englishman will return here, while there will also be recalls for the likes of Senne Lynen and Simon Adingra.
Rangers possible starting lineup:
McLaughlin; Tavernier, Goldson, Sands, Yilmaz; Matondo, Kamara, Lundstram, Jack, Tillman; Colak
Union SG possible starting lineup:
Moris; Sykes, Burgess, Van der Heyden; Nieuwkoop, Lynen, Teuma, Amani, Lapoussin; Vanzeir, Adingra
We say: Rangers 2-1 Union SG (Union SG 3-2 on aggregate)
Rangers are more than capable of turning this tie around in front of their own supporters, and the contest could quite easily head for extra-time. Union SG were so impressive in the first leg, though, and we believe that the Belgian outfit will just have enough to advance to the playoff round of the tournament.