What is a flock of turkeys called?

Annoying.

A group of turkeys = a board of directors who rubber stamp the CEO's every move. LOL

It's called a flock.

A feast?

Well,..Now , since you ask,..I believe , that , perhaps,..the answer to your question, might , depend upon the nature, of the "group" of turkeys that you are talking about,..For instance,..If you see a "group", of turkeys,..in the early spring,..then that will be 1 adult male, or a "Tom", with a group of females or "Hens", that the male, has gathered together, for mating, purposes,..I know that the "females", are referred to, collectively, as a "Harem", but I am not sure what you would call the "whole group, including the "Tom, ,..Then, in the summer you will see,a single adult female, or a "Hen", with a group, of partially grown "chicks",..You might call this a "Hen with her brood" Or a "Brood,.?" I don't Know. Then during fall & winter, the turkeys, will gather together, & large groups & will "Roost" together in a particular tree, which is called,.. a "roost",.& I believe that, as long as the turkeys are in that tree, that they are called a "roost" of turkeys,..So the question arises, Would you use the same word, in reference to each of these 3 different, "types", of groups of turkeys ,.?" I suspect that, technically speaking, perhaps you would call these 3 groups by different names,,,But I don't know for sure,.. I believe that "flock", will work, in some, but not in all cases,..for instance,..with regards to geese,..when the geese are on the ground, walking around, the "gaggle', seems right,..But when they are flying overhead,..then, "flock", seem more appropriate,..See what I mean,.?

They would not be called a flock but a "gagge" when they are grouped together.

Christmas Season :)

They are referred to as a "rafter" of turkey when in a group.

no, i believe it is known as a "F l u c k" but with a silent L.