1. Preheat oven to 350 degrees. Spray a baking sheet with olive oil cooking spray.
2. Rinse any dirt from the mushrooms and pat dry. Remove stems by twisting them off the cap so there is a cavity in the cap. Trim the edge of the cavity carefully to make more room for stuffing. Set caps aside. Finely chop the stems and trimmed bits.
3. In a large skillet, melt butter over medium heat. Add chopped stems, onion, and garlic; cook, stirring occasionally, until vegetables are softened, about 10 to 15 minutes. Remove from heat, add bread crumbs and Parmesan cheese, and stir to combine. Stir in the lemon juice, salt, pepper, and oregano and mix well. Add additional bread crumbs or lemon juice as needed to help the mixture hold together.
4. Stuff bread crumb mixture into reserved mushroom caps. Sprinkle each cap with mozzarella and drizzle lightly with olive oil. Arrange the caps on the prepared baking sheet and bake until cheese is melted and filling is lightly browned, about 15 minutes. Transfer to a platter, sprinkling with parsleyif desired, and serve warm.
Source: Hannaford fresh Magazine, November - December 2011