Finely chop the mushroom stems. Combine the chopped stems, the spinach, cheese, bread crumbs, scallion, wine, oregano, oil, salt, and pepper in a medium bowl.

With a small spoon, stuff each mushroom cap with about 1 tablespoon of the spinach mixture; place in a single layer in a 9 x 13-inch baking pan. (Can be made ahead) Cover and refrigerate up to 8 hours. Return to room temperature before baking.)

About 30 minutes before serving, preheat the oven to 375°F. Drizzle the water around the mushrooms in the pan.

Bake until the cheese is melted and the filling is hot, 15 – 20 minutes. Serve at once.