// Somewhere on top
    use Laravel\Passport\Client;

    // Overwrite method to take action after registration success
    protected function registered(Request $request, $user)
    {
        // Look for oAuth password grant client
        $client = Client::where('password_client', true)->firstOrFail();

        // Fill-in request with client data
        $request->request->add([
            'scope' => '*',
            'grant_type' => 'password',
            'client_id' => $client->id,
            'client_secret' => $client->secret,
            'username' => $request->email,
            'password' => $request->password
        ]);

        // Build request
        $tokenRequest = $request->create('/oauth/token', 'POST', $request->all());

        // Dispatch request
        $token = \Route::dispatch($tokenRequest);

        // Return result
        return $token;
    }