Step 1

Preheat the oven to 350F.

Step 2

Butter the 9x13-inch non-stick baking dish (just rub the end of a stick of butter all over the bottom and sides of the dish).

Step 3

Put butter in a microwave-safe bowl and melt in a microwave by heating it for 1-2 minutes.

Step 4

Whisk eggs in a large bowl. Add sugar, baking powder, salt, cinnamon and vanilla and mix until smooth.

Step 5

Add the milk and melted butter to the egg mixture and mix until combined.

Step 6

Add the oats to the egg mixture and stir until combined.

Step 7

Transfer the oatmeal mixture to the baking dish, and smooth the top with the back of a spoon. (At this point you can either refrigerate it ovenight and bake it in the morning, or bake immediately).

Step 8

Put in the oven and bake for 40-45 minutes, until fully set.

Step 9

Remove from the oven, cut into squares and serve warm.