When the Safari window opens in small format, position it in the upper left corner of the desktop, simply grab the lower right corner and drag it to widen and deepen the window to the size you want it to be. Then it will open every time in the new size you created by this action.

 

I have a laptop with an external monitor, when i am on the road then return home; i have the same issue.
but when safari opens I hold down the option key then click on the green button.. it will fill the screen, re size it to your choice. then quit and relaunch it should be fine.

 

I know how to resize the window, what I want is that Safari always opens with a full window. It seems that with the latest OS it does not unless I am overlooking something. It use to open with a full window until recently (i.e. the last few weeks)

Thanks for the suggestions.

 

I just stumbled across this quite by accident while surfing, but perhaps it is worth a try?

Go to System Preferences/General. Make sure "Close windows" when quitting an application is 'Unchecked'. Then open Safari/Go to Full Screen and quit. The next time you open Safari it should be in full screen.