This Loaded Baked Potato Casserole combines tender potatoes, smoky bacon, cheddar cheese, sour cream, ranch seasoning, and green onions in one creamy, cheesy dish. Baked until bubbly and golden, it's a delicious side for family dinners, barbecues, potlucks, and holiday gatherings.
Place the potatoes in a large stock pot and cover with water. Bring to a boil over high heat, then reduce to medium and cook for approximately 10–15 minutes, or until fork-tender. Drain thoroughly, rinse briefly with cool water, and allow to cool. Peel the potatoes if desired and cut into 1-inch chunks. Set aside.
Preheat oven to 350°F.
In a medium nonstick skillet, heat the vegetable oil over medium heat. Add the diced onion and cook until tender and translucent. Reserve ¼ cup of the uncooked bacon pieces for the topping, then add the remaining bacon to the skillet. Continue cooking until the bacon is browned and crisp. Drain excess grease.
Transfer the onion and bacon mixture to a large mixing bowl. Add the cooked potatoes. Reserve ¼ cup of chopped green onions and ¼ cup of shredded cheddar cheese for the topping. Add the remaining cheese and green onions, sour cream, mayonnaise, ranch seasoning, garlic powder, salt, and pepper. Gently fold together until evenly combined.
Lightly coat a 9 x 13-inch baking dish with nonstick cooking spray. Transfer the potato mixture to the dish, spreading evenly. Sprinkle the reserved cheese, green onions, and bacon over the top.
Bake uncovered for approximately 45 minutes, or until the casserole is hot, bubbly, and lightly golden. Make sure the bacon topping is fully cooked.
Remove from the oven and garnish with additional green onions or a drizzle of sour cream, if desired.