Preheat oven to 400 degrees and line a rimmed baking sheet with parchment paper.
Add perogies and onion a bowl and drizzle with oil and sprinkle with salt and pepper. Turn to coat and spread on pan.
Slice smoked sausages and add to the pan around the perogies and onions (we want the sausages evenly spread through the pan as they will render fat and flavor that will add to the perogies). Spread everything into a single layer as much as possible.
Bake for 25-30 minutes, turning perogies once half way through, until perogies are puffed and tender and onions are golden.
Serve as desired (my family loves it with sour cream!)