Preheat oven to 375°F.
Using a fork, stir together brown sugar, self-rising flour, and softened butter until crumbly.
Stir in oats and chopped pecans; set aside.
Whisk together flour and next 2 ingredients just until blended; whisk in melted butter.
Pour batter into a lightly greased 11- x 7-inch baking dish.
Top with banana slices, and sprinkle with streusel.
Bake at 375°F for 40 to 45 minutes or until golden brown and bubbly.
Serve with ice cream.
