A lot will depend on your particular chickens and what you have to offer them.  Sometimes if they're unfamiliar with a particular food item they won't eat it unless some bird gets brave & tries it first.  Some things they'll relish if it's cooked but not raw, and vice versa.  
Right now I have a lot of pumpkins I got from our church's pumpkin patch, sometimes I'll bake it but other times I'll feed it raw.
Sometimes I think it's better to NOT cut it up into chunks, there's a risk they can swallow too large a piece for their systems to manage.  If they peck it off themselves they'll have nice manageable beakfulls.  Also, it can keep them occupied pecking away at it all day, like a cabbage or corn on the cob.  
In our house there's a food heirarchy:  food is for the humans first, if it's unsuitable for humans it goes to the chickens, if unsuitable for them it goes to the compost pile, and only if unsuitable for the compost pile does it go into the garbage can.  Chickens can handle almost anything that's not too spoiled except for chocolate, and some folks say no avocado or potato skins, or at least green potato skins.  And they're better off without much junk food, things heavily salted or sugared.  Just like us.