Spray a 9x13 pan with cooking spray and set aside.
Preheat the oven to 350°.
In a mixing bowl, whisk flour, oats, sugar, and salt until combined. Add cold butter cubes and using a pastry blender (or a fork or your hands) cut the butter into the flour until you have large crumbs.
Measure out 1 cup of the mixture and set aside. Put the rest in the 9x13 pan and press firmly to make the crust. Use the bottom of a measuring cup to help make it even.
Bake the crust for 10-12 minutes. Then remove it from the oven.
Filling
Whisk together the eggs, sugar, yogurt, extract, and flour until well combined. Fold in the raspberries.
Pour the filling on top of the baked crust, and spread so it evenly covers the crust.
Sprinkle the remaining crumb mixture evenly on top.
Bake for 45 minutes.
Allow to cool about 30 minutes before cutting into squares and serving. Delicious as a stand alone, but feel free to serve warm with a dollop of vanilla ice cream or even whipped cream.
Notes
All purpose flour is recommended, I like King Arthur's unbleached flour.
Old Fashioned rolled oats are best for this recipe.
I always use unsalted butter, however if all you have is salted, then eliminate the salt in the recipe.
Sour cream can be substituted for the Greek yogurt.
Use the bottom of a jar or measuring cup to help even out the crust while pressing it into the pan.
A pastry blender works great for cutting in the butter. If you don’t have one, you can use a stand mixer, with the paddle attachment, or simply just your hands.
Almond extract is preferred as it really takes up the flavor on this recipe, however, vanilla extract can be substituted.
Frozen berries can be used in place of fresh. If you do this, make sure to fold in the frozen berries just before you add the filling to the crust.
If you are storing the bars in the fridge, and want to freshen them up before serving, place them in a 300° oven for about 10-15 minutes to crisp up the top.