In a large mixing bowl, beat the cream cheese and sugar with an electric mixer until smooth. Stir in the sour cream and vanilla and beat again until light and creamy.
Using a rubber spatula or wooden spoon, fold the grapes into the bowl of cream cheese mixture. Cover and chill until ready to serve. Right before serving, transfer to serving dish and sprinkle with brown sugar and pecans.
This recipe can be easily halved for a smaller crowd.
Use less cream cheese and sour cream if you'd like it less creamy.