1Heat oven to 350°F. Lightly grease 13x9-inch (3-quart) glass baking dish with shortening or cooking spray.
2In 3-quart saucepan, heat blackberries, 1 1/3 cups of the sugar and the butter to boiling over medium heat, stirring gently until butter is melted and sugar is dissolved. Remove from heat; set aside.
3In large bowl, beat cream cheese and remaining 2/3 cup sugar with electric mixer on medium speed until fluffy. Beat in milk until smooth. Stir in Bisquick mix and oats. Spread two-thirds of the cream cheese mixture (about 3 cups) in baking dish; spoon blackberry mixture evenly over top. Dollop remaining cream cheese mixture over blackberry mixture.
4Bake 35 minutes or until filling is bubbly and topping is golden brown. Serve warm with ice cream.