In a medium bowl, combine the crust ingredients and press into the bottom of a 9x13-inch pan. Place in the freezer while you make the filling.
In small saucepan, soften the gelatin in water; stir over low heat until the gelatin is dissolved.
In a large bowl, use an electric mixer to combine the cream cheese and sugar until well blended. Add the milk and the dissolved gelatin gradually. Mix until well combined. Mix in the Cool Whip. Remove 1½ cups of the mixture and put in another bowl. Carefully spoon the rest of the filling mixture into the pan on top of the crust. Add the remaining Oreo cookies to the rest of the mixture, spread on top, and refrigerate for at least an hour before serving.
Notes
One envelope of powdered gelatin (about 1/4 ounce) is about 2¼ to 2½ teaspoons.