Passed away at the age of 87.
That leaves:
Jamie Farr (90)
Alan Alda (89)
Mike Farrell (86)
Gary Burghoff (82)
Other M*A*S*H cast members:
McLean Stevenson (1996; 68)
Larry Linville (2000; 60)
Harry Morgan (2011; 96)
Wayne Rogers (2015; 82)
William Christopher (2016; 84)
David Ogden Stiers (2018; 75)
That leaves:
Jamie Farr (90)
Alan Alda (89)
Mike Farrell (86)
Gary Burghoff (82)
Other M*A*S*H cast members:
McLean Stevenson (1996; 68)
Larry Linville (2000; 60)
Harry Morgan (2011; 96)
Wayne Rogers (2015; 82)
William Christopher (2016; 84)
David Ogden Stiers (2018; 75)