Newchickenmom&kids :
They are outdoors and have been for weeks. They do enjoy eating the grass and whatever else they seem to find in the yard. We have them in a tractor which we move often. I wasn't feeding them the lettuce or bread for nutritional value but more because of all the stuff i've read in the threads about the kind of "treats" other chickens seem to like. Maybe they just need to be older...I don't know.
We started feeding our chicks organic veggies for treats when they were about 5 weeks old, so I don't think age has anything to do with it.
I wouldn't worry about them not eating treats. I think the reason your birds didn't go ga-ga for the treats was that they are already getting what they want - grass and juicy tidbits from the yard.
My flock's all-time favorite treat is plain yogurt w/active cultures with crushed garlic and chopped tomato in it.
About treats, my personal feeling is that they are like giving a small child sweets. It isn't something you do all the time, but in moderation is fine. As I've mentioned numerous times on this board, we provide a great variety of "treats" to our flock. Sometimes I think our birds eat better than we do, because they forage our farm from sunup to sundown. However, their 17% protein organic layer feed is the main source of their diet.
Most importantly, remember that everything they eat or are given to eat will affect the protein level in their diet.