Preheat your oven to 350°F (175°C) and grease an 8x8-inch baking pan or line it with parchment paper for easy removal.
In a large mixing bowl, combine the rolled oats, whole wheat flour, brown sugar, baking powder, and salt. Stir until well mixed.
In a separate bowl, whisk together the melted butter, honey (or maple syrup), and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and mix until just combined. The mixture will be crumbly.
Reserve about 1 cup of the oat mixture and press the remaining mixture firmly into the bottom of the prepared baking pan to form a crust.
In another bowl, combine the chopped strawberries and lemon juice, then spread the strawberry mixture evenly over the crust.
Crumble the reserved oat mixture over the strawberries, covering them completely.
Bake for 25-30 minutes or until the top is golden brown.
Allow the bars to cool in the pan for at least 15 minutes before slicing into squares. For best results, chill in the refrigerator for an hour before serving.