Peel and halve the onions and cut into thin slices. Finely dice the bacon. Wash the grapes well, pluck the stems and cut in half.
Heat the cooking oil in a saucepan and leave the diced bacon in it over medium heat. Add onions and sauté until translucent. Add butter and grapes and sauté for 1 - 2 minutes. Season to taste with salt and pepper.