Henry Domercant led five Olympiacos scorers in double-digits with 17 points and Ioannis Bourousis added 12 points and nine rebounds on 5-for-6 shooting.
The hosts led throughout, extending their advantage to a game-high 18 points several times in the fourth before closing out the win in Piraeus.
Greece, which hosts the final four in Athens, now has two teams in the Euroleague final eight.
Olympiacos' victory ended Partizan Belgrade's hopes of qualifying for the next round, as Partizan were demolished 55-86 on their home-court by defending champions CSKA Moscow in what ultimately ended up being an inconsequential match.
Maccabi Tel Aviv closed out their Top 16 with a 79-72 victory over Lottomatica Roma in another meaningless finale.
Maccabi will face CSKA in the quarter-finals in a replay of last year's Euroleague final, as Roma's European campaign is over.
"As far as we're concerned, even games that have no real value are important for our confidence," said Maccabi guard Lior Eliyahu.
"CSKA will be a completely different story. We need to change pace. We have players with amazing abilities and every one of them needs to give more in order to win in the next stage."
TAU Cerámica beat Pau-Orthez 93-75 to end the French champions' Euroleague campaign in an inconsequential loss.
In the other set of quarter-finals ULEB Cup champions Dynamo MoscowfacePanathinaikos and Unicaja Málaga face Barcelona in an all Spanish affair.
Follow LIVE coverage of the Euroleague quarter-finals starting on April 3 on www.eurosport.com.