Hmm...good question. This may be one you have to calculate, since I think sites like Yahoo typically list the forward PEG (based on five year earnings growth estimates). To get historical forward PEGs you would need the annualized earnings growth estimate at the start of a given year, as well as the P/E at the beginning of that year. Alternately, you could calculate historical PEG based on PE / Actual Growth. You can find a link on this from investopedia
here.