Geoffreys has appeared in several horror and teen films in the 1980s, most notably Heaven Help Us, as well as Fraternity Vacation and 976-EVIL with director/actor Robert Englund in 1989. He also played a supporting part in the critically acclaimed drama At Close Range in 1986. He is best known for playing the creepy "Evil Ed" in the 1985 vampire horror classic Fright Night starring Roddy McDowall, William Ragsdale, and Chris Sarandon. Two of Geoffreys' lines from that film became catch phrases in the mid-1980s: "To what do I owe this dubious pleasure?" and "You're so cool, Brewster!"
Geoffreys returned to horror in a supporting role as "Mr. Putski" in the independent film Sick Girl, released in October 2007. He went on to play a lead role in the horror film Do Not Disturb. Stephen later appeared in the horror film Emerging Past, which also featured actor Brooke McCarter of The Lost Boys fame.