Using a stand-up mixer, combine the oats, flour, brown sugar, baking powder, and cold butter. Mix on low until ingredients are incorporated. Portion out 1 3/4 cups and set aside. Pat down remaining oat mixture into bottom of 8x8 or 9x9 pan with the bottom of a clean measuring cup. Bake x 10 minutes.
Meanwhile, coarsely chop the blackberries using pulse mode on food processor or a manual food processor. Transfer to a medium bowl and add the honey, lemon juice, cornstarch, and chia seeds and stir.
Spoon blackberry mixture over crust evenly. Add the remaining crumb mixtures over the blackberries in spoonfuls. Spread it a bit to make it even and if desired leave a few spots without the crumb mixture to allow blackberries to show through. This is just for looks though. Bake x 30 minutes or until light golden brown. Allow to cool completely before cutting into bars.