I would invest in one of those bowls that has a protective cover on it that only opens when it senses a specific chip on the cat's collar. This way Bailey can eat at his own pace, and Oliver can't get into it even if he tried.
Then get the cats on a feeding schedule. Bailey can have access to his food on the floor, and you fill it at the same time as Oliver, but Oliver gets his food and once its gone its gone, he doesn't get more until dinner time. I would put Oliver's bowl in a place Bailey won't want to reach.
I agree with what another person said as well, if this is a very sudden change for Oliver, you should take him to the vet to be sure this isn't caused by a medical issue.
I would also take a look at what you are feeding. Low quality foods have a very small percentage of actual nutrition. What I mean by that, is that half a cup of Friskies dry food will contain just as much nutrition as a tablespoon of high quality wet food, like from Solid Gold or Wellness. If you are feeding a low quality food, this is mostly fillers, so your cats have to eat more to get the nutrients they need. Switch to a higher quality food, it is more nutrient dense so your cats will feel full longer. Oliver may feel hungry because he isn't getting the nutrition he needs, and is overeating because of it. Its a very common thing, you see it with pets and with people.