The singer -- wearing a sparkly top complete with a cape, leather leggings and heels -- sat for the entirety of her performance, making her growing bump stand out.
Barrett's husband, fellow Idol alum Cade Foehner, played guitar and sang backup vocals during her performance.
When ET spoke to Barrett in June, she opened up about quarantining with Foehner.
"Quarantine has been really good for us on a personal level and for our marriage," she said. "Being able to take time together to slow down and soak in everything that's happened over the last year or two has been wonderful. I'm grateful every day that he's my partner in life."
Watch the video below for more on Barrett.