I actually ended up calling Animal Poison control and spoke with a vet, she agreed that I had done the right thing with inducing vomitting and she did the calculation on how much onion he may have taken in vs his weight, I guess the danger area for a 28 Lbs dog is about 3/4 of a cup. Since she said that it sounds like he threw up most of it (She said normally when they throw up you only get about 80%) he will probably be okay but if I wanted to take that extra step to take him to the emergency room in the next few hours and have them give him Charcoal. Apparently when a dog ingest onions it isn't something that affects them immediatly, it breaks down the red blood cells and can actually take days to cause problems.
The charcoal has to be administered within the first few hours but I really feel that I got most of it out of him so I didn't take him and the Vet at the poison control center agreed.
So, we are getting ready to go to Banfield this morning to be checked out by our vet just to be on the safe side.
In case no one knows about the Animal Poison Control Center the number is 888-426-4435, they charge you a $55 fee but it was worth it to me to talk to a vet right away, not drive to go to an emergency vet and sit there for hours.
I'll let you guys know how it goes at the vet this morning. Thanks for the support last night!