Offer them fresh grass or veggies from the garden instead. If they are eating the peels then they are bored or lacking something. I can't say there is anything toxic in the peels but it really hasn't any nutritional value either so it would be better to have them eat something good for them and for the eggs.
Everything on my farm eats banana peel. I found out by mistake while chasing a heifer. I tried to tempt her with the banana and threw the peel about ten feet away. A few chickens were all over it, and soon after, so was she. Some of my goats will eat the peel but not the banana
I feed mine banana peels. I chop them up though because I had to chase a hen down that found one and got choked on it. She found a peel in the compost pile which is how I discovered that they love peels.