Put the oil, oregano or marjoram and garlic in a bowl. Season with freshly ground black pepper and whisk with a whisk or fork.
Halve the peppers lengthways and remove the seeds and all whites. Peel the potatoes and cut lengthways into approx. 1.5 cm thick slices.
Brush both lightly with the herb-oil mixture and spread out in one layer on baking sheets. Sprinkle with sea salt and bake for 40 minutes, until both are soft and are starting to turn brown around the edges. Let cool and arrange on a serving platter.
Add the balsamic vinegar to the remaining oil and spice mixture and drizzle over the salad.
Sprinkle everything with fresh oregano leaves and serve.