Heat the oven to 350 F.
Whisk all the dry ingredients together (flour, baking soda, matcha powder, and salt) in a medium bowl and set aside.
In a large bowl, mix the butter and sugar together.
Add the egg and vanilla extract, mix well.
Mix in the mashed banana and water. Beat until everything is incorporated.
Add the dry ingredients into wet ingredients. Mix together until they are all combined.
Add the oats and chocolate chips, mix briefly.
Line a cookie sheet with aluminum foil and coat lightly with cooking spray (I used coconut oil spray!). Use a spoon to scoop out the dough balls and place them onto the cookie sheet (1 inch apart).
Bake for 10 minutes or until golden.