Preheat your oven to 400°F (200°C).
In a large bowl, combine the sliced kielbasa, bell peppers, and onion.
Drizzle olive oil and sprinkle garlic powder, smoked paprika, salt, and pepper over the mixture.
Toss until everything is well coated, then spread the mixture evenly on a sheet pan.
Place the frozen pierogies atop the kielbasa and veggies on the sheet pan.
Bake for 25–30 minutes, stirring halfway through.
Remove from the oven and let cool slightly before serving.