Vernon finished fifth in the inaugural Australian Formula 4 Championship in 2015 before stepping back to a predominantly state program last year.
“I have spent the past year away from national level competition and have focused on developing my skill set in the Production Touring Cars,” said Vernon.
“I really want to thank Bruce Williams and (Aisin aftermarket manager) Richard Janssen for having the faith in me and giving me a chance to compete in this great high profile category.
“Hopefully (there's a) chance of great results in front of some important people in the sport.”
The 19-year-old's signing continues Williams' aim of fostering young talent, having fielded Ben Grice in the same entry last year.
The 2017 Toyota 86 Racing Series begins at the WD-40 Phillip Island 500 on April 21-23.