Avoiding cost of probate court

Once a Savings Bond is purchased, can you go back and list a co-owner? At my death, would this avoid having the Savings Bonds end up in court and go through the cost of probate? I just want to keep it simple and maybe make my two sons equal co-owners. Tom's response Savings Bond registrations can only have two names on them, so you can't make yourself owner and your sons equal co-owners. However, you can put one son's name on half your Savings Bonds and the other son's name on the other half. You can make your sons either co-owners or beneficiaries. You can do it either when you buy the bond or anytime thereafter. Both registration types avoid the costs of probate. The difference is that a co-owner can cash a bond anytime; a beneficiary can cash a bond only with the owner's death certificate.