Pawsy - the same thing has happened to me in the past with Scottrade, so now I always click aon (all or none). It doesn't seem to have an effect getting all the shares I want. Their policy is you won't be charged an extra commission if the fills take place in the same day, just if it carries over into subsequent days.
Register for free to join our community of investors and share your ideas. You will also get access to streaming quotes, interactive charts, trades, portfolio, live options flow and more tools.