Lots of discussion on this very topic here on the board. I graduated last May, and started orientation in an ER in September. I had 16 weeks orientation, and I have been on my own for almost 3 months now. There is lot to learn, and you have to know when to ask for help. If you have EMS experience, or have worked in an ER, it will be an advantage. I was a tech in the same ER for 2 years when I was in nursing school, and it has help tremendously in terms of knowing the flow of the department, knowing staff, and knowing what things are/where they are located.
So, in short-yes it is possible. I certainly think that the possibility of not doing well exists though. I am intellectually humble, and know when to ask for help. I have an extremely supportive group of seasoned staff around me, all willing to teach and help. I attribute my success thus far mostly to them. There are some in my orientation group (some who've been RN's for a number of years) that are not doing as well, but they don't have any ER experience. The pace is challenging for some, and the flow can throw people off.
I feel lucky to have had this opportunity! Good luck to you!