Juventus returned to the Champions League proper for the first time in three seasons after a 1-1 draw at Artmedia Bratislava gave the Italians a 5-1 aggregate win on Tuesday.
The twice European champions were joined in the lucrative group stages by Barcelona and Panathinaikos, who also eased through in the night's other two matches.
Barcelona chalked up a 4-1 aggregate win over Poland's Wisla Krakow despite a 1-0 defeat in the second leg while Panathinaikos beat Sparta Prague 1-0 in Athens to secure a 3-1 overall victory over the Czech side.
Another 13 teams will progress from Wednesday's third qualifying round matches to join the 16 who won automatic berths.
Former winners Liverpool and Olympique Marseille will have to tread carefully though.
Liverpool host Standard Liege after being held 0-0 in the first leg in Belgium while Marseille go into their home match with a 1-0 lead over Brann Bergen from the opening game in Norway.
Striker Branislav Fodrek volleyed Slovakians Artmedia into an early lead but Juventus, banned from European competition in 2006 for their involvement in an Italian match-fixing scandal, replied quickly with Amauri's headed equaliser from a Pavel Nedved cross.
"With a 4-0 advantage we were maybe a bit under par," Juve coach Claudio Ranieri told Rai television. "But we controlled the game. We wanted to win, we didn't want to lose."
Wisla downed 2006 winners Barcelona in the second leg thanks to a 52nd-minute goal by central defender Cleber.
Panathinaikos and Sparta missed several good chances before Brazilian striker Rodrigo Souza struck in injury time to delight the home fans at the Spyro Louis stadium.