Preheat your oven to 400F (200C) and line a large baking sheet with parchment paper.
Toss the frozen pierogies with the olive oil and garlic powder in a large bowl until evenly coated.
Spread the seasoned pierogies in a single layer across the prepared baking sheet.
Bake for 20 minutes, flipping them halfway through, until they are golden brown and crispy on the outside.
Push the crispy baked pierogies close together into the center of the baking sheet to form a mound.
Sprinkle the shredded cheddar cheese, mozzarella cheese, and crumbled bacon evenly over the hot pierogies.
Return the baking sheet to the oven for 5 minutes just until the cheese is completely melted and bubbling.
Remove from the oven and let the nachos rest on the pan for 5 minutes so the melted cheese can set up.
Drizzle the sour cream over the top and garnish with the diced tomatoes and sliced green onions before serving.
