Oakland Raiders draft pick Gareon Conley is telling investigators he did receive "brief oral sex" from his accuser on the night of the alleged sexual assault ... but insists it was consensual. 

We're told Conley says he was the recipient and that he did NOT force himself on the woman.

The former Ohio State football star is currently being investigated for rape -- after his accuser told police he sexually assaulted her in a Cleveland hotel room on April 9. 

Conley's attorney, Kevin Spellacy, says the two did engage in a "consensual sexual event" -- but says it was NOT intercourse.

The accuser told police they did have vaginal sex -- claiming he grabbed her, spun her around and raped her from behind. A rape kit was administered following the incident. 

Meanwhile, Conley met with police on Monday and provided a DNA sample and a voluntary statement.