In a large oven-proof skillet, cook sausage thoroughly, breaking it up as it cooks. Drain and transfer to bowl.
Wipe out skillet and heat oil in skillet. Add sweet potatoes sprinkled with cinnamon and cook for 5 minutes.
Add peppers and onions to pan and continue to cook for 3 more minutes.
Add sausage to pan, stir, then sprinkle cheese over top and let cook, without stirring, for 1-2 more minutes.
Season beaten eggs with salt & pepper and pour slowly over sausage-veggie mixture in pan.Let sit for 2 minutes then transfer skillet to oven.
Bake for 15-20 minutes.
Let cool slightly for easier cutting.
Notes
I placed the remaining 2 servings of the frittata in refrigerator to solidify then wrapped each serving in plastic wrap to freeze for breakfast during the week ahead. It takes about 2 minutes to reheat on a plate in the microwave. Perfect for grabbing on the way out the door for work.