Cut the kielbasa into 4 inch lengths and place into a large mixing bowl with the bell peppers, onions, olive oil, and seasonings stir well. Now add the pierogies in the bowl and stir to coat them in the seasonings.
Place the mixture onto a rimmed sheet pan lined with aluminum foil, spread out as even as possible.
Bake for 15 minutes then remove from the oven and flip everything over. Bake for an additional 10-15 minutes or until the pierogies are puffy and starting to get golden. Enjoy!