Prepare filling: Place all ingredients for filling in a medium saucepan over medium heat. Bring to a boil while stirring constantly until berries release their juices, then set aside to cool as you continue with recipe.
Prep: Preheat oven to 350°F and line an 8x8 inch pan with baking parchment, leaving an overhang.
Make oatmeal batter: Beat softened butter with both sugars in a large mixing bowl until creamy. Add egg and vanilla and beat just until fully incorporated. Evenly sprinkle flour, oats, baking powder and salt over creamed ingredients and fold in with a wooden spoon or rubber spatula until stiff batter forms.
Assemble bars: Spread ⅔ of batter in bottom of prepared pan. Spread with strawberry filling. Scatter remaining cookie dough in blobs on top.
Bake bars: Bake for around 25-35 minutes, or until bars are set and top is golden brown. Bars will still feel soft when done. Cool bars in pan on a wire rack on counter for at least 30 minutes before lifting out to slice.
Berries: Frozen strawberries will work, though I recommend letting them thaw a little first for easier slicing. Feel free to use different berries – I’ve even made these with diced apples before and they came out great. You might have to play a little with the amount of cornstarch you need to thicken the filling, but otherwise you are free to mix up the berry part as much as you like.
Flour: If you want to make these bars healthy (or healthier), you can use whole wheat flour in place of the plain flour. Even better if you have white whole wheat flour, as it tends to make more refined baked goods.
Sweetener: You can cut the sugar in the oatmeal base in half, if you’re looking to serve these as a breakfast.
Oats: I make this recipe with old fashioned rolled oats, and it’s the only way I have ever tested it. If you’re going to be using quick oats, please know that your results may differ.
Make sure to add enough “blobs” of dough/batter along the edges of the pan, especially the corners. This helps the bars to come out neater and they are easier to slice this way.