diff --git a/src/AbstractServer.php b/src/AbstractServer.php
index 828bee39..8439fa85 100644
--- a/src/AbstractServer.php
+++ b/src/AbstractServer.php
@@ -11,6 +11,8 @@
 
 namespace League\OAuth2\Server;
 
+use League\OAuth2\Server\Exception;
+use League\OAuth2\Server\TokenType\TokenTypeInterface;
 use Symfony\Component\HttpFoundation\Request;
 
 /**
@@ -32,6 +34,12 @@ abstract class AbstractServer
      */
     protected $storages = [];
 
+    /**
+     * Token type
+     * @var TokenTypeInterface
+     */
+    protected $tokenType;
+
     /**
      * Sets the Request Object
      * @param \Symfony\Component\HttpFoundation\Request The Request Object
@@ -72,4 +80,23 @@ abstract class AbstractServer
 
         return $this->storages[$obj];
     }
+
+    /**
+     * Set the access token type
+     * @param  TokenTypeInterface $tokenType The token type
+     * @return void
+     */
+    public function setTokenType(TokenTypeInterface $tokenType)
+    {
+        $this->tokenType = $tokenType;
+    }
+
+    /**
+     * Get the access token type
+     * @return TokenTypeInterface
+     */
+    public function getTokenType()
+    {
+        return $this->tokenType;
+    }
 }
diff --git a/src/Grant/AuthCodeGrant.php b/src/Grant/AuthCodeGrant.php
index 1494defe..e5f31624 100644
--- a/src/Grant/AuthCodeGrant.php
+++ b/src/Grant/AuthCodeGrant.php
@@ -218,19 +218,16 @@ class AuthCodeGrant extends AbstractGrant
             $session->associateScope($authCodeScope);
         }
 
-        $response = [
-            'access_token'  =>  $accessToken->getToken(),
-            'token_type'    =>  'Bearer',
-            'expires'       =>  $accessToken->getExpireTime(),
-            'expires_in'    =>  $this->server->getAccessTokenTTL()
-        ];
+        $this->server->getTokenType()->set('access_token', $accessToken->getToken());
+        $this->server->getTokenType()->set('expires', $accessToken->getExpireTime());
+        $this->server->getTokenType()->set('expires_in', $this->server->getAccessTokenTTL());
 
         // Associate a refresh token if set
         if ($this->server->hasGrantType('refresh_token')) {
             $refreshToken = new RefreshTokenEntity($this->server);
             $refreshToken->setToken(SecureKey::generate());
             $refreshToken->setExpireTime($this->server->getGrantType('refresh_token')->getRefreshTokenTTL() + time());
-            $response['refresh_token'] = $refreshToken->getToken();
+            $this->server->getTokenType()->set('refresh_token', $refreshToken->getToken());
         }
 
         // Expire the auth code
@@ -246,6 +243,6 @@ class AuthCodeGrant extends AbstractGrant
             $refreshToken->save();
         }
 
-        return $response;
+        return $this->server->getTokenType()->generateResponse();
     }
 }
diff --git a/src/Grant/ClientCredentialsGrant.php b/src/Grant/ClientCredentialsGrant.php
index cd0a6acf..786d5d2c 100644
--- a/src/Grant/ClientCredentialsGrant.php
+++ b/src/Grant/ClientCredentialsGrant.php
@@ -101,13 +101,10 @@ class ClientCredentialsGrant extends AbstractGrant
         $accessToken->setSession($session);
         $accessToken->save($this->server->getStorage('access_token'));
 
-        $response = [
-            'access_token'  =>  $accessToken->getToken(),
-            'token_type'    =>  'Bearer',
-            'expires'       =>  $accessToken->getExpireTime(),
-            'expires_in'    =>  $this->server->getAccessTokenTTL()
-        ];
+        $this->server->getTokenType()->set('access_token', $accessToken->getToken());
+        $this->server->getTokenType()->set('expires', $accessToken->getExpireTime());
+        $this->server->getTokenType()->set('expires_in', $this->server->getAccessTokenTTL());
 
-        return $response;
+        return $this->server->getTokenType()->generateResponse();
     }
 }
diff --git a/src/Grant/PasswordGrant.php b/src/Grant/PasswordGrant.php
index 4a1215df..9c2b27e3 100644
--- a/src/Grant/PasswordGrant.php
+++ b/src/Grant/PasswordGrant.php
@@ -137,19 +137,16 @@ class PasswordGrant extends AbstractGrant
             $session->associateScope($scope);
         }
 
-        $response = [
-            'access_token'  =>  $accessToken->getToken(),
-            'token_type'    =>  'Bearer',
-            'expires'       =>  $accessToken->getExpireTime(),
-            'expires_in'    =>  $this->server->getAccessTokenTTL()
-        ];
+        $this->server->getTokenType()->set('access_token', $accessToken->getToken());
+        $this->server->getTokenType()->set('expires', $accessToken->getExpireTime());
+        $this->server->getTokenType()->set('expires_in', $this->server->getAccessTokenTTL());
 
         // Associate a refresh token if set
         if ($this->server->hasGrantType('refresh_token')) {
             $refreshToken = new RefreshTokenEntity($this->server);
             $refreshToken->setToken(SecureKey::generate());
             $refreshToken->setExpireTime($this->server->getGrantType('refresh_token')->getRefreshTokenTTL() + time());
-            $response['refresh_token'] = $refreshToken->getToken();
+            $this->server->getTokenType()->set('refresh_token', $refreshToken->getToken());
         }
 
         // Save everything
@@ -162,6 +159,6 @@ class PasswordGrant extends AbstractGrant
             $refreshToken->save();
         }
 
-        return $response;
+        return $this->server->getTokenType()->generateResponse();
     }
 }
diff --git a/src/Grant/RefreshTokenGrant.php b/src/Grant/RefreshTokenGrant.php
index 1f5ee111..c84503c0 100644
--- a/src/Grant/RefreshTokenGrant.php
+++ b/src/Grant/RefreshTokenGrant.php
@@ -131,12 +131,9 @@ class RefreshTokenGrant extends AbstractGrant
         $oldAccessToken->expire($this->server->getStorage('access_token'));
         $newAccessToken->save($this->server->getStorage('access_token'));
 
-        $response = [
-            'access_token'  =>  $newAccessToken->getToken(),
-            'token_type'    =>  'Bearer',
-            'expires'       =>  $newAccessToken->getExpireTime(),
-            'expires_in'    =>  $this->server->getAccessTokenTTL()
-        ];
+        $this->server->getTokenType()->set('access_token', $accessToken->getToken());
+        $this->server->getTokenType()->set('expires', $accessToken->getExpireTime());
+        $this->server->getTokenType()->set('expires_in', $this->server->getAccessTokenTTL());
 
         // Expire the old refresh token
         $oldRefreshToken->expire($this->server->getStorage('refresh_token'));
@@ -148,8 +145,8 @@ class RefreshTokenGrant extends AbstractGrant
         $newRefreshToken->setAccessToken($newAccessToken);
         $newRefreshToken->save($this->server->getStorage('refresh_token'));
 
-        $response['refresh_token'] = $newRefreshToken->getToken();
+        $this->server->getTokenType()->set('refresh_token', $refreshToken->getToken());
 
-        return $response;
+        return $this->server->getTokenType()->generateResponse();
     }
 }
diff --git a/src/TokenType/AbstractTokenType.php b/src/TokenType/AbstractTokenType.php
new file mode 100644
index 00000000..d72181b7
--- /dev/null
+++ b/src/TokenType/AbstractTokenType.php
@@ -0,0 +1,41 @@
+<?php
+/**
+ * OAuth 2.0 Abstract Token Type
+ *
+ * @package     league/oauth2-server
+ * @author      Alex Bilbie <hello@alexbilbie.com>
+ * @copyright   Copyright (c) Alex Bilbie
+ * @license     http://mit-license.org/
+ * @link        https://github.com/thephpleague/oauth2-server
+ */
+
+namespace League\OAuth2\Server\TokenType;
+
+abstract class AbstractBearer
+{
+    /**
+     * Response array
+     * @var array
+     */
+    protected $response = [];
+
+    /**
+     * Set a key/value response pair
+     * @param string $key
+     * @param mixed  $value
+     */
+    public function set($key, $value)
+    {
+        $this->responsekey[$key] = $value;
+    }
+
+    /**
+     * Get a key from the response array
+     * @param  string $key
+     * @return mixed
+     */
+    private function get($key)
+    {
+        return isset($this->response[$key]) ? $this->response[$key] : null;
+    }
+}
diff --git a/src/TokenType/Bearer.php b/src/TokenType/Bearer.php
new file mode 100644
index 00000000..9b1acfaa
--- /dev/null
+++ b/src/TokenType/Bearer.php
@@ -0,0 +1,49 @@
+<?php
+/**
+ * OAuth 2.0 Bearer Token Type
+ *
+ * @package     league/oauth2-server
+ * @author      Alex Bilbie <hello@alexbilbie.com>
+ * @copyright   Copyright (c) Alex Bilbie
+ * @license     http://mit-license.org/
+ * @link        https://github.com/thephpleague/oauth2-server
+ */
+
+namespace League\OAuth2\Server\TokenType;
+
+class Bearer extends AbstractBearer implements TokenTypeInterface
+{
+    protected $response = [];
+
+    /**
+     * {@inheritdoc}
+     */
+    public function set($key, $value)
+    {
+        $this->responsekey[$key] = $value;
+    }
+
+    private function get($key)
+    {
+        return isset($this->response[$key]) ? $this->response[$key] : null;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function generateResponse()
+    {
+        $return = [
+            'access_token'  =>  $this->get('refresh_token'),
+            'token_type'    =>  'Bearer',
+            'expires'       =>  $this->get('expires'),
+            'expires_in'    =>  $this->get('expires_in')
+        ];
+
+        if (!is_null($this->get('refresh_token'))) {
+            $return['refresh_token'] = $this->get('refresh_token');
+        }
+
+        return $return;
+    }
+}
diff --git a/src/TokenType/Mac.php b/src/TokenType/Mac.php
new file mode 100644
index 00000000..b90d31da
--- /dev/null
+++ b/src/TokenType/Mac.php
@@ -0,0 +1,17 @@
+<?php
+/**
+ * OAuth 2.0 MAC Token Type
+ *
+ * @package     league/oauth2-server
+ * @author      Alex Bilbie <hello@alexbilbie.com>
+ * @copyright   Copyright (c) Alex Bilbie
+ * @license     http://mit-license.org/
+ * @link        https://github.com/thephpleague/oauth2-server
+ */
+
+namespace League\OAuth2\Server\TokenType;
+
+class Mac extends AbstractBearer implements TokenTypeInterface
+{
+
+}
diff --git a/src/TokenType/TokenTypeInterface.php b/src/TokenType/TokenTypeInterface.php
new file mode 100644
index 00000000..c0116ba8
--- /dev/null
+++ b/src/TokenType/TokenTypeInterface.php
@@ -0,0 +1,21 @@
+<?php
+/**
+ * OAuth 2.0 Token Type Interface
+ *
+ * @package     league/oauth2-server
+ * @author      Alex Bilbie <hello@alexbilbie.com>
+ * @copyright   Copyright (c) Alex Bilbie
+ * @license     http://mit-license.org/
+ * @link        https://github.com/thephpleague/oauth2-server
+ */
+
+namespace League\OAuth2\Server\TokenType;
+
+interface TokenTypeInterface
+{
+    /**
+     * Generate a response
+     * @return array
+     */
+    public function generateResponse();
+}