Preheat your oven to 350 °F and grease a baking dish with cooking spray. Arrange your oven racks so that one is towards the bottom and one is towards the top.
Pour the mixture onto your greased baking dish and spread it out into an even, thin layer. Press it down with a spatula to make sure the mixture is sticking together.
Bake the granola for about 10 minutes on the top rack of your oven. Then, without stirring the granola, move it to the bottom rack to bake for another 10-15 minutes or until slightly golden brown.
Remove the granola from the oven and allow it to cool completely* before breaking it into clusters and storing it in an airtight container at room temperature for up to a month.
Notes
*Allowing the granola to cool completely is crucial for forming clustery granola. As the granola cools, the oat mixture sticks together and hardens to form crunchy clusters!