Green’s Dictionary of Slang

turkey adj.1

[? turkey n.1 (4a)]

1. (US) easily accomplished and enjoyed or desired.

[US]H.C. Witwer Smile A Minute 101: Joe, our gang goes into the thing yellin’ and singin’, and it don’t make no difference how warm the scrap gets, it’s turkey to them. Why, Joe, when they get hit you gotta almost chain ’em in the hospital, or they’ll sneak out on the doctors and get in it again.

2. (US gang) cowardly.

[US]W. Brown Run, Chico, Run (1959) 16: O.K., am I turkey? I like the moolah as much as you. Let’s pull a score.
[US]W. Brown Monkey On My Back (1954) 63: He turned turkey the rumble (street fight) we had with the Dukes. I always reckoned he was chicken.