Preheat the oven to 375°F and line an 8"x8" baking pan with parchment paper.
In a large bowl, mix together the rolled oats, flour, lemon zest, and baking powder. Add maple syrup and combine.
Gently press a little less than two-thirds of the dough onto the bottom of the prepared baking pan. Bake for 12 minutes.
Crush berries to make a jam like texture. Spoon this over the still warm crust and sprinkle the remaining oat mixture over the berries.
Bake for another 25 minutes or until the top has lightly browned and the filling is bubbly.
Remove from the oven and let the bars cool completely. Refrigerate for 2 hours before cutting.
Enjoy.