Bayern are now within touching distance of the final that Munich's Allianz Arena will host on May 19 as they look to win the Champions League trophy for the second time and claim their fifth European Cup title overall.
Croatian Olic was back in the hero role, two years after his hat-trick in Lyon put Bayern through to the 2010 final, where they lost 2-0 to Inter Milan in Madrid.
"We were very concentrated, despite the amount of games we are playing at the moment," said Bayern coach Jupp Heynckes, whose side contenders for a Champions League, Bundesliga and German Cup treble.
"In the first half, (goalkeeper) Manuel Neuer rescued us a few times. After that we came back stronger and deserved the win.
"Marseille weren't in the quarter-finals for nothing and they tried everything."
Bayern were missing suspended Germany star Bastian Schweinsteiger and Heynckes opted to leave in-form pair Mario Gomez and Arjen Robben – the goal-scorers from the first leg - on the bench.
Germany's Thomas Müller started on the right, with Olic in front of Toni Kroos in the attacking midfield role.
Having lost the first leg 2-0 in Marseille last Wednesday, the visitors were always facing an uphill task to win in Munich.
"At half-time, I didn't ask my players to score four goals," said Marseille coach Didier Deschamps.
"We had to show honour and pride in the last 45 minutes. Of course we tried to score, but we had to stop them playing too."
First-choice goalkeeper and captain Steve Mandanda was back from suspension and endured a busy night, while midfielder Alou Diarra was suspended.
He was replaced by Benoit Cheyrou, with Brazilian striker Brandao up front
and top scorer Loic Remy on the right flank.
"We lost to a great team, but we did not give up," said Remy.
"Hats off to Bayern, I hope they go all the way. We still have the League Cup final to look forward to and we want to do well in the league."
Marseille had a good early chance when Cheyrou found his way through the Bayern defence and teed up Jeremy Morel to shoot, forcing Neuer into a low save.
The opening goal came on 13 minutes when Franck Ribery found space down the right wing and his cross was converted by Olic for his first goal for two months and then another at 37 minutes.
The second half was mainly a dull affair with Bayern cruising into the last four and Marseille doing their best to frustrate the Germans.
With the Bavarians having won 4-0 on aggregate, Bayern will now host the first
leg of their semi-final on April 17 and will probably play Real Madrid.