Preheat toaster oven to 350°F (or 'Bake' if it doesn’t let you set temp).
In a bowl, mix 1½ cups oats, 1 cup flour, 1 tsp salt, 1 tsp baking powder, ½ tsp baking soda, and optional ½ tsp cinnamon.
In another bowl, whisk 1 cup milk or water, 1 egg, and 2 tbsp oil or butter.
Stir wet into dry until just combined — thick, scoopable batter.
Grease your pan lightly and spread batter evenly (about ¾–1 inch thick).
Bake 25–30 minutes, until the top looks set and a knife comes out mostly clean.
Let cool at least 10–15 minutes before slicing (this matters for texture).
If your toaster oven runs hot cover loosely with foil after 15 minutes or drop temp slightly if you can