In a medium bowl, combine graham cracker crumbs and melted butter. Press the mixture into the bottom of a 9x13 inch baking dish to form a crust.
In a large bowl, beat together the softened cream cheese, powdered sugar, and vanilla extract until smooth. Gently fold in 1 cup of whipped topping until well combined. Spread this cream cheese mixture evenly over the graham cracker crust.
In a separate bowl, dissolve the strawberry Jell-O in 2 cups of boiling water. Stir until fully dissolved, then add 2 cups of cold water. Allow the mixture to cool slightly.
Layer the mixed berries over the cream cheese layer in the baking dish. Pour the cooled Jell-O mixture over the berries, ensuring they are evenly covered.
Refrigerate for at least 4 hours or until the Jell-O is fully set. Once set, top with the remaining whipped topping before serving.