Like a lot of owners, I like to give my 'tiels a special treat of a hard-boiled egg once a month or longer. The egg is a chicken's egg, hard-boiled and mashed with a fork.
There is always a lot of egg left over. Would a QUAIL egg be okay to give under the same specifications?
(background: they are on Tidymix seed mix on recommendation from their avian vet, they get some garlic sticks sometimes, or a fruit stick. I hand-feed a little millet at times to encourage hand-feeding, and their veg is baby carrots and broccoli, with some spinach if there are bags available)
I would think quail eggs would be fine if you have access to them. If you have to buy them I imagine they would be expensive. When I give Bennie eggs, I just give him some and eat the rest myself. I have given him hard-boiled eggs and sometimes other cooked eggs when I make eggs for breakfast. If you don't like eggs or are allergic, that wouldn't work though!