In a large cast-iron skillet, heat 3 tablespoons of olive oil over medium-high heat. Add the sliced potatoes to the pan and cook until golden brown and cooked through about 10-12 minutes. Transfer cooked potatoes to bowl and set aside.
Using the same pan, add the remaining 1 tablespoon of olive oil and the sliced sausage. Cook over medium heat until the sausage is brown on all sides, about 5 minutes.
Add the sliced onions and cook for an additional 2-3 minutes, or until the onions begin to soften. Add the potatoes back to the pan and mix everything together. Continue cooking over medium heat until the potatoes are reheated.
Notes
*The Nutritional Facts that have been calculated on this recipe are only estimates.