Heat oven to 325 degrees and line a 9X9-inch baking pan with aluminum foil so that it overhangs the edges. This will make it easy to remove the bars. Spray the foil with cooking spray.
To make the crust, combine flour, oats, brown sugar, baking powder, and salt in a medium bowl. Add melted butter and stir to combine.
Press half of mixture firmly into the pan. Bake for approximately 8 minutes, or until light brown. Cool.
To make the filling, whisk together flour, sugar, coffee granules, and salt in a bowl.
Place chocolate chips and butter cubes in a large microwave-safe bowl. Microwave at 20 second intervals, stirring in between, until melted and smooth.
Whisk eggs into chocolate mixture. Stir in flour mixture.
Pour chocolate filling over cooled crust and top evenly with remaining oatmeal mixture.
Bake 35 to 40 minutes. Cool for at least 1 hour before slicing.