In a large bowl, combine condensed milk, lemon juice and zest. Stir in yogurt and marshmallows. Fold in the whipped topping.
Pour half of yogurt mixture into a 9 x 13 pan, and sprinkle with half of the strawberries and blueberries. Cover with the remaining yogurt mixture, and decorate the top with the remaining blueberries and strawberries.
Cover with plastic wrap and freeze for at least 6 hours or until firm. Remove from the freezer 45-60 minutes before serving. Cut into squares and serve.
Notes
Let it thaw at least for 45 minutes for best results. Hard frozen berries don't give off much taste, so the thaw is necessary.
Make sure the berries and strawberries are small and thinly sliced to make it easier for kids to eat, since it is frozen hard.
Keyword Blueberry Dessert, No Bake Dessert, Patriotic Dessert