People.com said the actresses attended a development meeting Friday at the CBS Studio Center Lot near Los Angeles.
The former Beverly Hills, 90210 co-stars were there to discuss playing exaggerated versions of themselves in an-as-yet-untitled show CBS is working on.
Beverly Hills, 90210 -- the young-adult soap Spelling's late father Aaron co-created -- initially ran 1990 to 2000. Spelling and Garth reprised their roles of Donna and Kelly in the reboot 90210, which had a new cast and was broadcast 2008-13.
"#back2work great creative day yesterday with my #partnerincrime @jenniegarth #90210vibes #donnaandkellyforver #besties," Spelling captioned a photo she posted on Instagram Saturday.
The image showed the actress in her car in the studio parking lot.
Spelling and Garth also worked together on the sitcom Mystery Girls, which was canceled in 2014 after only one season.