I learned the hard way that even cooked onion is VERY bad for dogs. I had made some burgers with cooked onions for a picnic and of course, my buddy got what I dropped. That night, and the next day, she was vomitting at least once every hour. I was scared out of my mind. I hated seeing her like this because of what I gave her. I looked for lists of poisons (a day late) and found onions to be worse for dogs than chocolate. Unfortunately, chocolate is the one that has the worst reputation. I've actually known people to give Snickers to their search and rescue dogs (also Dobies) as rewards. I wouldn't suggest this without a vet's OK, but it is not a death sentence for a dog to eat milk chocolate. The danger correlation is with the increased amount of cocoa concentrated (the darker, the worse). Long story short, keep the onions away from the dogs. I'm sorry I don't have that list I refered to, but you should be able to find it with a search engine.