Preheat your oven to 425°F (220°C). Line a large baking sheet with parchment paper or foil.
Place the sliced chicken sausages, peppers, zucchini, and red onion on the sheet pan.
Drizzle everything with olive oil, then sprinkle on the garlic powder, Italian seasoning, salt, and pepper.
Toss everything with your hands—yes, it’s messy, but it’s worth it—until evenly coated.
Spread the mixture into a single layer, making sure nothing’s overcrowded (we want roasting, not steaming).
Bake for 25–30 minutes, flipping halfway through, until the veggies are tender and slightly charred around the edges.
Remove from the oven, sprinkle with fresh parsley, and serve warm. Try not to eat it all straight from the pan.