The original 1975 cast of SNL consisted of:

• Dan Aykroyd
• John Belushi
• Chevy Chase
• George Coe
• Jane Curtin
• Garrett Morris
• Laraine Newman
• Michael O'Donoghue
• Gilda Radner

www.saturday-night-live.com has a complete list of casts from each season, but I thought it would be more useful to list the additions and subtractions each year:

1976

• Left: George Coe and Michael O'Donoghue
• Joined: Bill Murray

• Left: Chevy Chase
• Joined: Tom Davis and Al Franken

• Joined: Don Novello

• Left: Dan Aykroyd, John Belushi
• Joined: Harry Shearer, Peter Aykroyd, Jim Downey, Brian Doyle-Murray, Tom Schiller, Paul Shaffer and Alan Zweibel.

• Left: everyone
• Joined: Denny Dillon, Robin Duke, Gilbert Gottfried, Tim Kazurinsky, Gail Matthius, Eddie Murphy, Joe Piscopo, Ann Risley, Charles Rocket, Tony Rosato, Yvonne Hudson, Mitchell Kriegman, Matthew Laurance, Laurie Metcalf, Emily Prager and Patrick Weathers

• Left: Denny Dillon, Gilbert Gottfried, Gail Matthius, Ann Risley, Charles Rocket, Yvonne Hudson, Mitchell Kriegman, Matthew Laurance, Laurie Metcalf, Emily Prager and Patrick Weathers
• Joined: Christine Ebersole and Mary Gross
• Returned: Brian Doyle-Murray

• Left: Christine Ebersole, Tim Kazurinsky, Brian Doyle-Murray and Tony Rosato
• Joined: Brad Hall, Gary Kroeger and Julia Louis-Dreyfus

• Joined: Jim Belushi

• Left: Robin Duke, Brad Hall, Eddie Murphy and Joe Piscopo
• Joined: Billy Crystal, Christopher Guest, Rich Hall, Harry Shearer, Martin Short and Pamela Stephenson

• Left: everyone
• Joined: Joan Cusack, Robert Downey Jr., Nora Dunn, Anthony Michael Hall, Jon Lovitz, Dennis Miller, Randy Quaid, Terry Sweeney, Danitra Vance, A. Whitney Brown, Al Franken, Don Novello, Dan Vitale and Damon Wayans

• Left: Joan Cusack, Robert Downey Jr., Anthony Michael Hall, Randy Quaid, Terry Sweeney, Danitra Vance, Al Franken, Don Novello, Dan Vitale and Damon Wayans
• Joined: Dana Carvey, Phil Hartman, Jan Hooks, Victoria Jackson, Jon Lovitz, Kevin Meaney and Kevin Nealon

• Left: Kevin Meaney
• Returned: Al Franken

• Joined: Mike Myers and Ben Stiller

• Left: Ben Stiller

• Left: Nora Dunn and Jon Lovitz
• Joined: Chris Farley, Al Franken, Tim Meadows, Chris Rock, Adam Sandler, Rob Schneider, David Spade and Julia Sweeney

• Left: Jan Hooks, Dennis Miller and A. Whitney Brown
• Joined: Beth Cahill, Ellen Cleghorne, Siobhan Fallon, Melanie Hutsell and Rob Smigel

• Left: Victoria Jackson, Beth Cahill and Siobhan Fallon

• Left: Dana Carvey and Chris Rock
• Joined: Michael McKean, Norm Macdonald, Jay Mohr and Sarah Silverman

• Left: Phil Hartman, Melanie Hutsell, Rob Schneider, Julia Sweeney and Sarah Silverman
• Joined: Morwenna Banks, Chris Elliott, Janeane Garofalo, Mark McKinney, Laura Kightlinger, Molly Shannon

• Left: nearly everybody -- Morwenna Banks, Ellen Cleghorne, Chris Elliott, Chris Farley, Janeane Garofalo, Michael McKean, Mike Myers, Kevin Nealon, Adam Sandler, Al Franken, Laura Kightlinger and Jay Mohr
• Joined: Jim Breuer, Will Ferrell, Darrell Hammond, David Koechner, Cheri Oteri, Nancy Walls, Chris Kattan , Colin Quinn and Fred Wolf

• Left: David Koechner, David Spade and Nancy Walls
• Joined: Ana Gasteyer and Tracy Morgan

• Left: Mark McKinney and Fred Wolf

• Left: Jim Breuer, Norm Macdonald
• Joined: Jimmy Fallon, Chris Parnell and Horatio Sanz

• Joined: Rachel Dratch and Maya Rudolph

• Left: Tim Meadows, Cheri Oteri and Colin Quinn
• Joined: Tina Fey and Jerry Minor

• Left: Chris Parnell, Molly Shannon and Jerry Minor
• Joined: Dean Edwards, Seth Meyers, Amy Poehler and Jeff Richards