Heat the olive oil over medium heat in a 3-quart saucepan for about one minute, add the sliced Italian sausage and spread into a single layer. Let brown slightly, then turn to brown the second side, about 3 – 4 minutes. Add the diced onion and minced garlic and stir to combine. Continue cooking over medium heat until the onion turns translucent. Do not over brown, be especially watchful of the garlic.