I don't feed Oats as a treat, but as a food, course they think its a treat.
I mix up my own scratch 2 parts oats, 1 milo, 1 cracked corn and then add in some sunflower seeds and flax seeds. Oats is very good for egg laying, I have a winter slow down but have never been without eggs, not even during molt. I feed them scratch Morning and Evening, then they go eat their Layer food before bed time. I use race horse oats because its less dusty than the other oats, I tried the crimped but like the Race Horse Oats better. Personal preferance. If you have layers, give them oats. They may not eat them the first time, but they will if given again.
I give my chicks and ducklings Oatmeal (regular, instant or steel cut), with Milo, Millet, Amaranth, Buckwheat, Cracked Corn and Flax seed run through a coarse grind. They get the baby mix from 4 weeks till they start getting into the larger grains when they are in with the hens at about 12 weeks old. Though when they are older they don't get ground up unless I have more babies around. There are usually babies around most of the year. Come to think of it, they like the steel cut better than the oatmeal flakes, but will eat either.
With 20+ hens, plus ducks, plus chicks I go through 100 lb of oats, 50 lb each of Milo and Cracked Corn every 12 weeks or less. Their scratch is close to 50% of their food and they have 4 hours of yard time every day, and will have most of the day in the out in the yard with the hot weather coming.
Oh, in the winter, when I make Oatmeal, I just make extra for the hens and chicks if I have any at the time. Mixed with some scrambled egg and yogurt --a hens delight. Just drop the pie pans quickly and step back. If you don't they will fly up and knock them out of your hands. This has happened on occasion, when I am just to slow.