The Grammy-winning songwriter and producer, 68, joked about his fortuitous introduction with McPhee, 34, on the set of American Idol when she was a contestant and he was a guest mentor in 2006.
“I was bragging!” Foster said laughingly as he spoke with Access Hollywood on Thursday.
During season 5, Foster worked with McPhee as she prepared to sing Whitney Houston’s “I Have Nothing,” which he helped write. “Katharine’s got a great, great future ahead of her,” he said of McPhee’s singing talents at the time.
The Waitress actress, who was persuaded by ex-husband Nick Cokas to compete on the Fox show, eventually finished as the runner-up to Taylor Hicks.
And she later collaborated with her soon-to-be husband for a few live performances, including his 2008 PBS tribute concert Hit Man: David Foster & Friends.
Though they consistently avoided addressing dating rumors, McPhee and Foster were first romantically linked in May 2017 when the two were spotted enjoying a PDA-filled dinner date at Nobu in Malibu.
But in May, the couple finally confirmed they were indeed an item when they attended the Met Gala together. PEOPLE confirmed their engagement on July 3.
Recently, McPhee defended her fiancé on Twitter with a clapback that had her fans and followers take notice. “Y’all should be worrying more about registering to vote and midterm elections than who’s marrying me,” she wrote Friday, adding, “Thank you for coming to my TED talk.”
Then on Sunday, she was back for more, thanking her fans for their support. “Ok my fans have been making SEVERAL points in my mentions and I’ve loved reading all your comments. Thanks for defending me & doing all this dragging lol. Love you all.”
This will be the fifth marriage for Foster, who was most recently wed to Real Housewives of Beverly Hills star Yolanda Hadid.