Fry bacon until crisp. Drain and crumble into mixing bowl, reserving 2 teaspoons of drippings. Saute onion and green pepper in bacon drippings until onion is opaque. Remove from heat and stir in garlic, parsley, oregano, salt, and pepper. Mix well and add to crumbled bacon in bowl. Stir in clams and cheese. Spoon into mushroom caps, rounding the filling. Place on baking sheet and bake at 350 degrees F for about 20 minutes, until mushrooms are tender. (Or microwave at 50-percent power for 8 to 10 minutes.) Serve hot.