In a medium bowl, combine chopped strawberries, sugar, and lemon juice. Set aside to macerate for about 10 minutes.

Preheat the oven to 350°F (175°C) and grease a baking dish.

In a large mixing bowl, combine rolled oats, whole wheat flour, brown sugar, baking powder, and salt.

Add melted butter, egg, and vanilla extract to the dry ingredients and mix until well combined.

Press half of the oatmeal mixture into the bottom of the prepared baking dish.

Spread the strawberry filling evenly over the base.

Crumble the remaining oatmeal mixture on top of the strawberries.

Bake in the preheated oven for 25-30 minutes, or until the top is golden brown.

Allow to cool before cutting into bars.