I adapted this comforting dessert from a recipe my mother-in-law gave to me. Hers fed a family with nine growing kids who were never full, so there was never any left. There aren't any leftovers when I make my downsized version, either! —Marliss Lee, Independence, Missouri
Place blackberries in a greased 1-qt. baking dish. In a small bowl, combine the sugar, cornstarch, water and lemon juice until smooth. Pour over berries. Combine the oats, flour, brown sugar and cinnamon; cut in butter until crumbly. Sprinkle over berries.
Bake, uncovered, at 375° until filling is bubbly, 20-25 minutes. Serve warm with ice cream.