Preheat the oven to 350 degrees. Line a 9x13 baking dish with parchment paper or spray with non-stick spray.
In a medium bowl, combine the flour, oats, sugar, brown sugar, and baking powder. Mix well.
In a small bowl combine the melted butter and vanilla, and mix into the flour sugar mixture until the consistency is crumbly. Reserve 1 1/2 cups of the oat mixture and set aside.
Press the remaining mixture into the bottom of the prepared baking dish.
Gently spread the jam over the crust, being careful not to break the crust as you spread.
Sprinkle the reserved oat mixture over the top of the jam.
Bake uncovered for 30 minutes or until the top is golden brown.
Let bars cool completely before preparing the glaze.
To make the glaze, whisk together the powdered sugar, milk, and vanilla until smooth. Drizzle over the bars.