The TrevorLive event brought together leading gay celebrities to raise awareness and bring in donations to support the charity's work with young members of the lesbian, gay, bisexual, transgender (Lgbt) community who are in crisis.
Star Trek actor Quinto and Juno star Ellen Page, who went public with her sexuality earlier this year (14), were among the speakers at the event, along with Harris, who attended with his partner David Burtka, and Modern Family star Ferguson, who was with his producer husband Justin Mikita.
Other attendees included actor Cheyenne Jackson and his fiance Jason Landau.
After the bash, Harris took to Twitter.com to write, "Had such a wonderful time tonight at TrevorProject Live. So impressed by this organisation. Please support them, or at least learn more."
The event was hosted by comedienne Wanda Sykes, while The Huffington Post creator Arianna Huffington was honoured with the Trevor Hero Award for her work in support of gay rights.