Preheat your oven to 375°F. Spray a 9x13-inch baking dish with non-stick spray or coconut oil.
Whisk the egg. Then add the egg along with all the remaining ingredients to a large bowl and stir with a large spoon or spatula until all the ingredients are well incorporated.
Pour them in o your prepared baking dish.
Bake uncovered for 30 to 35 minutes.
The oats are cooked through after 25 to 30 minutes it just depends how toasted you want the top to be. As well, cooking them longer will dry them out more if you want a cake-like texture. As with anything else that you bake, time depends on if your oven has been calibrated and the size and color of the baking pan that you use. (I bake them for 30 minutes, turn the oven off, and allow them to set inside the hot oven for another 5 minutes.)
Remove the baked oats from the oven and allow them to cool 5 minutes before serving. Serve plain or with syrup.
Refrigerate leftovers in an airtight container for up to 1 week. Reheat in the microwave.
They also freeze well. I recommend cutting them into squares, wrapping, and freezing them individually. You can reheat for a few seconds in the microwave.