In 2004 Gregory guested as Rohan Shanley in an episode of Blue Heelers.[4] Two years later, he played the recurring role of Garrett Burns, a love interest for Rachel Kinski (Caitlin Stasey), in the soap opera Neighbours.[6]
He made his feature film debut in Jon Hewitt's Acolytes.[4] He plays Mark, a teenager who becomes involved in murder and violence.[4] Principal photography on the film began in April 2007 in Queensland.[4] Gregory's band, Menace, had two songs featured on the soundtrack.[7] Shortly after, Gregory was cast in Beautiful a film by writer-director Dean O'Flaherty.[2][8] Of his role as Danny in the film, Gregory told Sacha Molitorisz of The Sydney Morning Herald "I always seem to be playing a weird, freaky kid. But there's something really beautiful about Danny."[2] For his portrayal of Danny, Gregory earned a nomination for Best Young Actor at the 2009 Australian Film Institute Awards.[9]
Gregory was cast in the regular role of JB Deekes in the children's television series The Elephant Princess in 2008.[4][10] His Menace bandmates made a cameo appearance in episode seven of The Elephant Princess and one of their tracks was also featured.[3] In June 2008, Gregory joined the cast of the dark comedy film Accidents Happen,[8] which is based on a semi-autobiographical screenplay by Brian Carbee.[11] Gregory originally auditioned for a different role, but the filmmakers thought he would be perfect for the character Doug Post instead.[5] Accidents Happen was shot in Sydney and released in 2009.[11][12]
In 2011, Gregory starred alongside Isabel Lucas in the Australian musical comedy film A Heartbeat Away.[8][13] In April 2012, it was announced Gregory had re-joined the supporting cast of Neighbours as "mathematics genius" Ed Lee.[6] He was contracted for four-months and began appearing from 8 June 2012.[6][14] Gregory then appeared in Return to Nim's Island, which was filmed on the Gold Coast in August 2012.[15]
Gregory played drummer Dylan James in the 2017 supernatural thriller American Satan. The role was later recast to James Cassells for the television spin-off Paradise City.[16] He also stars as a struggling artist amidst the American heroin epidemic in the 2018 drama film Shooting in Vain.[17]