Spears left Kankakee for California during the early 1980s, to pursue a career in acting. He landed small roles in the mainstream films Trading Places and Blow Out. Spears was seen in three mainstream films under the name Gregory Patrick. In the 1988 comedy Sexpot he played the role of Damon; the same year he appeared in the horror comedy Critters 2: The Main Course. A year later, Spears starred, along with Georgina Spelvin and Linda Blair, in Bad Blood, a gothic thriller also known as A Woman Obsessed. He also acted in commercials and in a one-week stint on Ryan's Hope in 1989 where he played a bartender. Spears recalls this time as being "fun".

Spears was introduced to the industry in 1987 by Ona Zee. In a 2016 interview, he said he was an aspiring actor who, after a few years in show Business, fell on hard times due to the 1988 Writers Guild of America strike. He said he turned to modeling when a make-up Artist handed him her card and told him to dial the number if he ever felt like doing nude work. With nothing more than a can of beans and a can of potatoes in his cupboard, he called a month later, despite his concern that working in the adult entertainment industry could hurt his professional career later on. Spears said he felt conflicted after his first shoot, for which he earned $400. Still, he fielded and accepted more offers, which came in, he said, once producers noticed he had some acting experience. Initially, he kept his mother uninformed about his new profession. Spears' first billing was as detective Hank Smith in The Case of the Sensuous Sinners, released in 1988. In 1990, Spears and Tom Byron traveled to Australia and made the films Singles Holiday, Lost in Paradise, Dial a Sailor, Sexual Healer and Outback Assignment. The same year, he won the Adult Video News Best Actor Award for his performance in The Masseuse with Hyapatia Lee. Spears also played Captain Jim Quirk in the "Sex Trek" series, which was a sex-parody of Star Trek. He has since been inducted into the AVN Hall of Fame.

He was best friends with the late Jon Dough, with whom he entered the Business at around the same time. Spears expressed that Dough was "like a brother" to him. Following Dough's suicide in 2006, Spears and his wife set up a memorial fund on MySpace to help pay for the funeral costs.

In 2009, Spears provided the voice of a character called John Q. Mind in the episode "In Country...Club", the fifth-season premiere of American Dad!.

In 2011, he shot his last film in the pornography film industry, having broken down in tears as he left the set. He publicly announced in 2015 that he had left the industry, turning to Christianity.

In a 2015 interview, Spears said that he had severe drug problems during his time in the adult Business and that a vicious circle kept him in the Business all those years: "I had to go to work, to do the porn, so that I could buy the drugs, to bury the pain of doing the porn. So I’d go to work, and do the porn, so I could buy the drugs, to bury the pain. And around and around it went." Spears also claimed that the Business changed his view of women, perceiving them as sexual objects, adding "I lost the ability to have a loving and caring relationship. I thought I was still able. I was fooled."