Preheat the oven to 350°F. Line a 13x9-inch baking pan with parchment paper then grease it with cooking spray.
In a medium bowl, whisk together the mashed bananas, eggs, milk, olive oil and vanilla extract.
In a separate large bowl, whisk together the flour, brown sugar, baking powder, cinnamon and salt.
Add the wet ingredients to the bowl with the dry ingredients and stir just until combined, then stir in 3/4 cup chocolate chips.
Pour the batter into the greased baking pan, spreading it into an even layer. Sprinkle the remaining 1/4 cup chocolate chips on top.
Bake the bars until a toothpick inserted comes out clean, 20 to 25 minutes. Remove the bars from the oven and let them cool completely in the pan before slicing and serving.