Blend banana, eggs, oats, and baking powder in a blender until smooth, about 45 seconds.
Spray a griddle or skillet with cooking spray and heat over medium-high heat.
Drop batter by large spoonfuls onto the griddle and cook until bubbles form and the edges are dry, 3 to 4 minutes. Flip and cook until browned on the other side, 2 to 3 minutes. Repeat as necessary.