What to do when an older cat is used to grazing on her food, while a younger one has started to over eat?

Two cats: Bailey is 15 years old, and Oliver is about 5. We found him in the road as a kitten and failed at rehoming him (lol). Bailey has grazed on her food throughout the day her whole life. Oliver was a grazer for a while, but lately its like he's been binging on the food and even sometimes throws up from... show more Two cats: Bailey is 15 years old, and Oliver is about 5. We found him in the road as a kitten and failed at rehoming him (lol). Bailey has grazed on her food throughout the day her whole life. Oliver was a grazer for a while, but lately its like he's been binging on the food and even sometimes throws up from eating too much.
There's not really a place to leave Bailey's food out all day where Oliver can't reach it so I'm not sure what to do. At 15 years old, I doubt Bailey is willing to change her ways. Is there a way to retrain Oliver to not gorge himself on food?
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