Olivia Wilde Won't Talk About Harry Styles Salad Dressing, Urges People To Vote

Olivia Wilde ain't gonna talk about her elusive salad dressing ... but she does have an important message that she wants the whole world to know.

We got Olivia Thursday at Tracy Anderson's fitness studio in Brentwood, CA ... takin' off after getting a good sweat in. Of course, there was one thing on our photog's mind -- even if it wasn't on Olivia's.

We try and get some answers about her making some more of that dressing, but mum's the word ... instead, she's hoping for people to get out there and vote in the U.S. midterms, coming up in just a few weeks.

As we reported -- OW's former nanny, Erika Genaro, told DailyMail of an incident when Olivia was whipping up her special salad dressing, getting ready to go see Harry Styles for a dinner date -- which allegedly triggered Jason Sudeikis.

After the nanny story spread, Olivia posted an excerpt from Nora Ephron's memoir "Heartburn" which details a salad dressing ... which many believe to be the one Olivia made.