Spinach Mushroom Hobo Pack

1 pound small fresh white mushrooms
1 large red onion, cut in thin wedges
1 10-ounce jar artichoke hearts, drained
2 large garlic cloves, thinly sliced
2 tablespoons olive oil
1 (10-ounce) bag spinach

Preheat grill or oven to 425 degrees. Lay two sheets of heavy-duty foil, each 24 inches long, one on top of each other. Trim mushroom stems. Combine mushrooms, onion, artichoke hearts and garlic in the center. Drizzle with olive oil. Arrange spinach leaves on top. Lay a third length of heavy-duty foil on the top. Fold the edges of the foil sheets to securely close the pack. Grill or cook on the center rack in the oven or until vegetables are tender, about 25 minutes. Serve over slices of grilled or toasted Italian or French bread. Yields four appetizer servings.