Chop the potatoes, peppers, and onions to desired size (I made the potatoes a little larger than the peppers and onions.)
In a large skillet over medium heat, combine 2 Tablespoons butter and 2 Tablespoons oil. Heat until butter is fully melted.
Add chopped onions and peppers; sauté for 5 minutes, stirring occasionally. Add the minced garlic and sauté until fragrant.
Add the potatoes, salt, and pepper. Push the mixture down firmly with a spatula or wooden spoon, then cover and cook for 5 minutes.
Uncover, add the remaining butter and oil, and increase heat to medium-high. Stir the mixture every 5 minutes, letting the potatoes brown, until they're golden and crispy on the edges. Potatoes are done when fork tender.