diff --git a/oauth2client/appengine.py b/oauth2client/appengine.py
index 5439a35..c747528 100644
--- a/oauth2client/appengine.py
+++ b/oauth2client/appengine.py
@@ -126,12 +126,10 @@
     """Constructor for AppAssertionCredentials
 
     Args:
-      scope: string or list of strings, scope(s) of the credentials being
+      scope: string or iterable of strings, scope(s) of the credentials being
         requested.
     """
-    if type(scope) is list:
-      scope = ' '.join(scope)
-    self.scope = scope
+    self.scope = util.scopes_to_string(scope)
 
     super(AppAssertionCredentials, self).__init__(
         'ignored' # assertion_type is ignore in this subclass.
@@ -157,7 +155,8 @@
       AccessTokenRefreshError: When the refresh fails.
     """
     try:
-      (token, _) = app_identity.get_access_token(self.scope)
+      scopes = self.scope.split()
+      (token, _) = app_identity.get_access_token(scopes)
     except app_identity.Error, e:
       raise AccessTokenRefreshError(str(e))
     self.access_token = token
@@ -399,7 +398,7 @@
     Args:
       client_id: string, client identifier.
       client_secret: string client secret.
-      scope: string or list of strings, scope(s) of the credentials being
+      scope: string or iterable of strings, scope(s) of the credentials being
         requested.
       auth_uri: string, URI for authorization endpoint. For convenience
         defaults to Google's endpoints but any OAuth 2.0 provider can be used.
@@ -419,7 +418,7 @@
     self.credentials = None
     self._client_id = client_id
     self._client_secret = client_secret
-    self._scope = scope
+    self._scope = util.scopes_to_string(scope)
     self._auth_uri = auth_uri
     self._token_uri = token_uri
     self._user_agent = user_agent
@@ -647,7 +646,7 @@
 
     Args:
       filename: string, File name of client secrets.
-      scope: string or list of strings, scope(s) of the credentials being
+      scope: string or iterable of strings, scope(s) of the credentials being
         requested.
       message: string, A friendly string to display to the user if the
         clientsecrets file is missing or invalid. The message may contain HTML
diff --git a/oauth2client/client.py b/oauth2client/client.py
index dc9bc89..cce4ae6 100644
--- a/oauth2client/client.py
+++ b/oauth2client/client.py
@@ -775,7 +775,7 @@
       Args:
         service_account_name: string, id for account, usually an email address.
         private_key: string, private key in P12 format.
-        scope: string or list of strings, scope(s) of the credentials being
+        scope: string or iterable of strings, scope(s) of the credentials being
           requested.
         private_key_password: string, password for private_key.
         user_agent: string, HTTP User-Agent to provide for this application.
@@ -790,9 +790,7 @@
           token_uri=token_uri,
           )
 
-      if type(scope) is list:
-        scope = ' '.join(scope)
-      self.scope = scope
+      self.scope = util.scopes_to_string(scope)
 
       # Keep base64 encoded so it can be stored in JSON.
       self.private_key = base64.b64encode(private_key)
@@ -936,7 +934,7 @@
   Args:
     client_id: string, client identifier.
     client_secret: string, client secret.
-    scope: string or list of strings, scope(s) to request.
+    scope: string or iterable of strings, scope(s) to request.
     code: string, An authroization code, most likely passed down from
       the client
     redirect_uri: string, this is generally set to 'postmessage' to match the
@@ -973,7 +971,7 @@
 
   Args:
     filename: string, File name of clientsecrets.
-    scope: string or list of strings, scope(s) to request.
+    scope: string or iterable of strings, scope(s) to request.
     code: string, An authorization code, most likely passed down from
       the client
     message: string, A friendly string to display to the user if the
@@ -1024,7 +1022,7 @@
     Args:
       client_id: string, client identifier.
       client_secret: string client secret.
-      scope: string or list of strings, scope(s) of the credentials being
+      scope: string or iterable of strings, scope(s) of the credentials being
         requested.
       redirect_uri: string, Either the string 'urn:ietf:wg:oauth:2.0:oob' for
           a non-web-based application, or a URI that handles the callback from
@@ -1039,9 +1037,7 @@
     """
     self.client_id = client_id
     self.client_secret = client_secret
-    if type(scope) is list:
-      scope = ' '.join(scope)
-    self.scope = scope
+    self.scope = util.scopes_to_string(scope)
     self.redirect_uri = redirect_uri
     self.user_agent = user_agent
     self.auth_uri = auth_uri
@@ -1169,7 +1165,7 @@
 
   Args:
     filename: string, File name of client secrets.
-    scope: string or list of strings, scope(s) to request.
+    scope: string or iterable of strings, scope(s) to request.
     redirect_uri: string, Either the string 'urn:ietf:wg:oauth:2.0:oob' for
         a non-web-based application, or a URI that handles the callback from
         the authorization server.
diff --git a/oauth2client/gce.py b/oauth2client/gce.py
index d1b1234..ad27588 100644
--- a/oauth2client/gce.py
+++ b/oauth2client/gce.py
@@ -53,12 +53,10 @@
     """Constructor for AppAssertionCredentials
 
     Args:
-      scope: string or list of strings, scope(s) of the credentials being
+      scope: string or iterable of strings, scope(s) of the credentials being
         requested.
     """
-    if type(scope) is list:
-      scope = ' '.join(scope)
-    self.scope = scope
+    self.scope = util.scopes_to_string(scope)
 
     super(AppAssertionCredentials, self).__init__(
         'ignored' # assertion_type is ignore in this subclass.
diff --git a/oauth2client/multistore_file.py b/oauth2client/multistore_file.py
index c919573..b8e9ff0 100644
--- a/oauth2client/multistore_file.py
+++ b/oauth2client/multistore_file.py
@@ -69,7 +69,7 @@
     filename: The JSON file storing a set of credentials
     client_id: The client_id for the credential
     user_agent: The user agent for the credential
-    scope: string or list of strings, Scope(s) being requested
+    scope: string or iterable of strings, Scope(s) being requested
     warn_on_readonly: if True, log a warning if the store is readonly
 
   Returns:
@@ -83,8 +83,7 @@
         filename, _MultiStore(filename, warn_on_readonly=warn_on_readonly))
   finally:
     _multistores_lock.release()
-  if type(scope) is list:
-    scope = ' '.join(scope)
+  scope = util.scopes_to_string(scope)
   return multistore._get_storage(client_id, user_agent, scope)
 
 
diff --git a/oauth2client/util.py b/oauth2client/util.py
index bda14c6..8166d39 100644
--- a/oauth2client/util.py
+++ b/oauth2client/util.py
@@ -27,6 +27,7 @@
 import gflags
 import inspect
 import logging
+import types
 
 logger = logging.getLogger(__name__)
 
@@ -125,3 +126,22 @@
   else:
     args, _, _, defaults = inspect.getargspec(max_positional_args)
     return positional(len(args) - len(defaults))(max_positional_args)
+
+
+def scopes_to_string(scopes):
+  """Converts scope value to a string.
+
+  If scopes is a string then it is simply passed through. If scopes is an
+  iterable then a string is returned that is all the individual scopes
+  concatenated with spaces.
+
+  Args:
+    scopes: string or iterable of strings, the scopes.
+
+  Returns:
+    The scopes formatted as a single string.
+  """
+  if isinstance(scopes, types.StringTypes):
+    return scopes
+  else:
+    return ' '.join(scopes)
diff --git a/tests/test_oauth2client_appengine.py b/tests/test_oauth2client_appengine.py
index 6039a0d..827a31f 100644
--- a/tests/test_oauth2client_appengine.py
+++ b/tests/test_oauth2client_appengine.py
@@ -175,7 +175,9 @@
     apiproxy_stub_map.apiproxy.RegisterStub(
       'memcache', memcache_stub.MemcacheServiceStub())
 
-    scope = ["http://www.googleapis.com/scope"]
+    scope = [
+     "http://www.googleapis.com/scope",
+     "http://www.googleapis.com/scope2"]
     credentials = AppAssertionCredentials(scope)
     http = httplib2.Http()
     credentials.refresh(http)
@@ -183,8 +185,18 @@
 
     json = credentials.to_json()
     credentials = Credentials.new_from_json(json)
-    self.assertEqual(scope[0], credentials.scope)
+    self.assertEqual(
+      'http://www.googleapis.com/scope http://www.googleapis.com/scope2',
+      credentials.scope)
 
+    scope = "http://www.googleapis.com/scope http://www.googleapis.com/scope2"
+    credentials = AppAssertionCredentials(scope)
+    http = httplib2.Http()
+    credentials.refresh(http)
+    self.assertEqual('a_token_123', credentials.access_token)
+    self.assertEqual(
+      'http://www.googleapis.com/scope http://www.googleapis.com/scope2',
+      credentials.scope)
 
 class TestFlowModel(db.Model):
   flow = FlowProperty()
diff --git a/tests/test_oauth2client_util.py b/tests/test_oauth2client_util.py
new file mode 100644
index 0000000..6c72521
--- /dev/null
+++ b/tests/test_oauth2client_util.py
@@ -0,0 +1,27 @@
+"""Unit tests for oauth2client.util."""
+
+__author__ = 'jcgregorio@google.com (Joe Gregorio)'
+
+import unittest
+
+from oauth2client import util
+
+
+class ScopeToStringTests(unittest.TestCase):
+
+  def test_iterables(self):
+    cases = [
+      ('', ''),
+      ('', ()),
+      ('', []),
+      ('', ('', )),
+      ('', ['', ]),
+      ('a', ('a', )),
+      ('b', ['b', ]),
+      ('a b', ['a', 'b']),
+      ('a b', ('a', 'b')),
+      ('a b', 'a b'),
+      ('a b', (s for s in ['a', 'b'])),
+    ]
+    for expected, case in cases:
+      self.assertEqual(expected, util.scopes_to_string(case))