"I actually can't remember it," she said of the moment, appearing on the "The Graham Norton Show".
"The great thing about the Oscars is there is a bar just behind (the auditorium), so everyone is there. There are hundreds of seat fillers, so almost everybody is in the bar getting bladdered!" added Olivia, according to a report in femalefirst.co.uk.
While the 2018 film "Tha Favourite" catapulted Olivia to big-ticket Hollywood, she has been balancing the big screen projects with small screen assignments.
The actress will soon return to the small screen as Queen Elizabeth in series three of "The Crown". After bagging the role, she even met Prince William and thought he was "very charming and lovely".
Olivia, however, was disappointed to learn that the Prince does not watch the show, which is based on the life of his grandparents, Queen Elizabeth and Prince Philip.
"I met Prince William at a dinner and he asked what I was doing at the moment before he quickly added, 'Actually, I know what you're doing'.
"I was so excited and asked, 'Have you watched it?' His answer was a firm, 'No.' But he was very charming and very lovely," Olivia said.
( With inputs from IANS )