The Welsh singer, who made the live shows of the TV talent contest in 2009, will be at the shopping centre on Thursday 10 November for the big festive bash.
Lucie will perform several songs while local girl Melissa Murdoch and cool country duo Raintown will also sing to what is sure to be a bumper crowd.
St Andrew's Boys' Club will also be putting in an appearance and showing off their football tops, sponsored by the Oak Mall.
Lucie, from Pentrych in Wales, shot to fame after she amazed judges in her X Factor audition with a fantastic version of Whitney Houston's smash hit 'I Will Always Love You'.
She sailed through the first rounds of the competition, was put into the live shows by her mentor, Dannii Minogue, and was tipped as a possible winner until she was controversially voted out in favour of Irish twins Jedward.
Following her performances on the show, she won a part in Les Miserables at the Queen's Theatre in London, playing the part of Cosette alongside US pop sensation Nick Jonas.
On the day of her Oak Mall visit, Lucie will be joined by top DJs for the official start of the countdown to Christmas from 3.30pm - with the big lights switch on taking place at 5pm.
Her appearance is another coup for the mall after X Factor's Lloyd Daniels wowed crowds during last year's Christmas switch-on.