Preheat oven to 400ºF.
Heat a large skillet over medium-high heat with 1 turn of the pan of EVOO. Cook kielbasa until brown and crispy, about 3-4 minutes. Remove the sausage from the pan with a slotted spoon and set aside.
Add the hash brown potatoes into the same pan with the sausage drippings and cook until brown and crispy, about 4-5 minutes.
While the hash browns are crisping, place a medium-size skillet over medium-high heat with one turn of the pan of EVOO. Add the onions, garlic, salt and freshly ground black pepper and cook until tender, 5-6 minutes.