I'd like to know the answer, too, cuz as far as I knew you couldn't watch quicktime in fullscreen unless you bought the quicktime pro player.
You can download the free version where you can maximize the video in a window. It's not fullscreen, but it's close. I would take the window, but I don't know how to get from the video stream to the Quicktime player. If I had the direct URL to the video I could view it maximized, but I don't know how to get the URL either. Why can't it be easy like Real Player.
I don't think you can do it with streaming video. I've seen a lot of movie trailers in Quicktime and I've had to stay in whatever frame it came in.
I wasn't thinking before, but I went to where the video was downloaded to in the temporary internet files and I got the video and played it in the regular quicktime player and maximized the window. Thanks anyway!! I don't think it can be maximized while it's streaming on a site either. If you find out though, let me know!!