I just had the same problem. Not many similar problems to be found and no solution. This is strange because this seems to be a missing config option 'global/request/direct_front_name', which isn't set in Core/Oauth module. How can all the tutorials work without this important setting!?
Without "oauth" setting being there, every call to /oauth/[controller] leads to "noRouteAction" being resolved (see. Mage_Core_Controller_Request_Http::setPathInfo() and Mage_Core_Controller_Request_Http::isDirectAccessFrontendName($storeCode)) instead of default indexAction.
So, the solution is to set this setting in local config or an own extension as follows
<?xml version="1.0"?>
<config>
[...]
<global>
[...]
<request>
[...]
<direct_front_name>
<oauth/>
</direct_front_name>
</request>
</global>
</config>
Afterwards you can finally get the token at least. I'm checking the further process now.