In a nonstick pan, add 2 tablespoons of oil and heat over medium-high heat. Add the diced onions and cook until they are translucent and slightly golden, or about 5 minutes.
Add the diced baked potatoes, garlic, and bell pepper, and toss with a spatula until everything is coated in the oil. Season with salt and pepper, and toss again.
Using a spatula, flip the potatoes over and cook until golden again, repeating this process 3–4 times until they are completely golden brown on all sides.
Once your potatoes are almost completely cooked, add the ham and bacon bits and toss them so that they warm through before removing the hash browns from the heat.
Off the heat, add 1 ½ cups of shredded cheddar cheese and mix, then top with the remaining ½ cups of cheese and cover with a lid for a few minutes until it melts.