Preheat oven to 350°F
In a small saucepan, heat olive oil over medium heat. Add the onions. Allow to soften for five minutes and then put aside.
Make sure your hash browns are thawed. They will take longer to bake if they are not thawed. To speed up the process, you can freeze them.
Let them air dry to remove excess water.
Keep 1 cup cheddar cheese aside
Mix all ingredients together in a large bowl.
Put it in a 9x13 casserole dish greased and then top with the remaining cheese.
Bake for 35 minutes covered.
Turn heat up to 400°F. Bake an additional 5-10 mins, or until the top is slightly crispy.
Take out of the oven and allow to cool for 10 minutes before serving.
