Preheat the oven 400F, or heat your barbecue grill to medium-high heat.
Take 4, 12-inch long sheets of aluminum foil, and divide the potatoes among each piece in a single layer. Top with zucchini and olives, making a pile in the center of each piece of foil. Drizzle with olive oil, and season with salt and pepper.
Top each pile of vegetables with a salmon filet, and sprinkle with the oregano and garlic. Top with a slice of lemon.
Seal the foil packets tightly, crimping the seams to prevent the juices from leaking.
Place the packets on a baking tray (if using the oven), or on the grill, and cook for 25 to 30 minutes, or until the vegetables are tender.