Preheat oven to 180 °C.
Roughly chop onions and cube red and green capsicums.
Heat 2 tbsps olive oil in a non stick pan, add onions and sauté. Cube potatoes and add to the pan. Slice garlic and add. Add red and green capsicums and toss.
Add salt, peppercorns and toss again.Drain the tinned corn and transfer into an ovenproof dish. Add the sautéed vegetables and mix. Pour the white sauce over the vegetables. Sprinkle breadcrumbs and cheese.
Drizzle tomato ketchup in a zig zag pattern and keep the dish in the preheated oven and bake for 10-15 minutes. Serve hot.