Heat oil in a skillet over medium heat.
Add onions and cook for 2-3 minutes.
Add bell pepper, and cook an additional 2-3 minutes, until onions and peppers are soft.
Add garlic and cook for 1-2 minutes, stirring to ensure garlic does not burn.
Stir potatoes into the skillet, along with salt and pepper. Cook for 15-20 minutes, until potatoes are tender and crispy. Stir every few minutes so that the onions and peppers do not burn.
Stir in leftover corned beef, and cook until the corned beef is warm and crispy, about 3-4 minutes. Garnish with chopped fresh parsley and serve.