Grind oats in a blender until fine. Whisk oat flour, all-purpose flour, baking powder, cinnamon and salt in a bowl.
Whisk mashed bananas, eggs, milk, vanilla and 1 tablespoon oil in another bowl. Fold into the dry mixture and let stand for 5 minutes.
Heat a nonstick griddle over medium heat and brush lightly with some of the remaining oil. Cook about 1/4 cup batter per pancake for 2 to 3 minutes until bubbles form and edges look set, then flip and cook for 1 to 2 minutes until the centers are fully set; make about 12 pancakes in batches.
Freeze after cooking: cool pancakes briefly on a rack, refrigerate within 2 hours and chill completely. Stack with parchment between them, place in a freezer bag, label and freeze for up to 2 months.
Reheat from frozen: arrange 3 pancakes on a microwave-safe plate, cover with a damp paper towel and microwave for 45 seconds, turn and continue in 20-second bursts until their centers reach 165°F.
Crisp warmed pancakes in a dry skillet over medium heat for about 30 seconds per side if desired. Serve 3 per portion with 1 tablespoon maple syrup.