ASP.NET Web Api: The requested resource does not support http method 'GET'

If you have not configured any HttpMethod on your action in controller, it is assumed to be only HttpPost in RC. In Beta, it is assumed to support all methods - GET, PUT, POST and Delete. This is a small change from beta to RC. You could easily decore more than one httpmethod on your action with [AcceptVerbs("GET", "POST")].

All above information is correct, I'd also like to point out that the [AcceptVerbs()] annotation exists in both the System.Web.Mvc and System.Web.Http namespaces.

You want to use the System.Web.Http if it's a Web API controller.