Lightly brush an 8 x 8 casserole dish with olive oil or avocado oil.
Preheat your oven to 350 degrees f.
Heat 1 Tablespoon of oil in a large skillet over medium heat. Add in onions, garlic, and bell pepper, then sauté for 2-3 minutes.
Add in the sweet potatoes and continue to cook over medium heat, until they begin to soften about 10-12 minutes.
Remove from heat and transfer to a casserole dish.
In a large bowl, whisk the eggs, with the milk, shredded cheese, and seasonings.
Pour your egg mixture over the sautéed veggies in the casserole dish. (You can make this ahead, and store covered in the fridge for up to 24 hours)
Bake for 35-40 minutes or until a knife inserted in the center comes out clean and sweet potatoes are tender.
Once your casserole is finished baking, allow it to cool for a bit, then slice and serve.
Enjoy!