20Sep/100
Make Quicktime autoplay movies on a Mac
Simple! It's a shame there is no preference setting for it, but this isn't particularly difficult!
"Here’s what to do – first you go into Terminal. If you don’t know how, just invoke Spotlight and search for terminal and launch it from there.
In Terminal, write (or copy/paste) the following line:
defaults write com.apple.QuickTimePlayerX MGPlayMovieOnOpen 1
Hit Enter."
From: How To: QuickTime X Autoplay Movies On Open In Snow Leopard — TechPatio