Add 20 day moving averages to the possible performance factors
Add 20 day moving averages to performance display
You can do that yourself. Select "indicators" then Simple Moving averages, then type in the period you want. You can do a chart with only one MA or two or three MAs. They can be any periods you want. The problem is that Yahoo won't save them for you. Vote yes on the suggustions to allow your chart settings to be saved.