"I've quit the show," he told reporters at Wednesday night's We're The Millers premiere. "I have done five seasons, I've had three break-ups, I've come out as bisexual… I've done all that and I've decided the party's over for me.
"But I'll never close the door fully," he added. "There are lots of other projects in mind and people are talking. It's terrifying to be leaving the show as it's all I have known on TV."
The 28-year-old is one of the show's original cast members and has experienced many ups and down during its five series.
He has been through three break-ups. The first was with Gabriella Ellis, an aspiring singer who quit the show after the fourth series.
Ollie then started dating Topshop heiress Chloe Green but called the relationship off after a few months of dating. Chloe is now with Jennifer Lopez's former husband Marc Anthony.
His last on-screen relationship was with co-star Ashley James. The pair dated for several months but parted ways due to Ashley's growing concerns about Ollie's sexuality.
He also admitted that he will miss his best friends Cheska Hull and Binky Felstead, who have been signed on for the sixth series.
"I will miss every aspect of the show and everyone it, it was a family," he said.
Ollie wrote a non-fiction book earlier this year entitled Laid In Chelsea. He revealed that he hopes to follow up his debut offering with a novel about relationships.
"I love the idea of relationships," he said. "I brought a book out this year and it did well so I've started writing fiction – my first ever novel I'm trying to do at the moment. We're also discussing shows.'
The sixth series of the E4 show will air later this year.