Quintana (4-8, 4.49 ERA with the White Sox) will start against Baltimore right-hander Ubaldo Jimenez (4-4, 6.67) three days after being acquired in a deal with the cross-town White Sox.
The Cubs gave up four big prospects for Quintana, and he's hoping to do big things for his new team.
"I'm not surprised that (the White Sox) moved me, but I didn't know where I'd go," Quintana said. "I'm so happy I moved to the other side of the city and stayed in Chicago. I'm really happy. I think it was the best situation for me."
The left-hander will wear No. 62 with the Cubs. He started slowly but has done better in the past six weeks, going 2-1 with a 2.70 ERA since June 1.
Quintana has a 1-5 career record with a 4.65 ERA against the Orioles.
As for Jimenez, he has been inconsistent throughout the season. Some times he's been very good, others very bad.
He got the victory July 9 versus the Twins in an 11-5 game but allowed four runs on four hits in five innings.
The entire starting rotation has stumbled for much of this season, and are looking for someone to help right the ship and take pressure off the bullpen.
Kevin Gausman (eight runs in three innings) and Wade Miley (seven runs in 4 2/3 frames) combined to allow 15 runs in the first two games of this series as Baltimore has yet to slow down a Cubs' team which hit only .239 in the first half.
Jimenez is 1-3 with a 5.14 career record versus the Cubs (45-45).
Cubs manager Joe Maddon wants his team to start the second half better, and they've already done well with two wins, 19 runs and eight homers versus Baltimore in the first two games.
Still, he's saying it's a bit early to really push his team although Maddon has a good feeling about where his team is at with the second half just underway.
"If you get the whip out too soon right now, man, you will be done by the middle of August," Maddon said. "That's my experience. Right now, my sense is ... they're starting to catch a second wind."
For the Orioles, the bullpen is their strength when it comes to pitching, and the recent returns of Zach Britton and Darren O'Day help.
Britton did not pitch Saturday, and manager Buck Showalter said he's moving closer to make the left-hander his closer.
Still, Brad Brach pitched well during most of Britton's time on the disabled list, and the skipper said he's going to be careful with how he uses everyone in that part of the bullpen
"We've got multiple options there I feel comfortable with," Showalter said. "It allows me not to over-use somebody, which we haven't done and won't do."
Right now, the Orioles need to find some consistency from the starting rotation. That might be a tall task as Showalter hasn't found it all year, and the team has slipped to six games under .500 at 42-48, tying a season-worst.