In a medium bowl, stir together ground pork mushrooms, bread crumbs, oregano, salt and pepper. Shape mixture into 4 patties.
Grill or broil patties 5 to 7 minutes per side or until no longer pink inside. Always cook ground pork to well done.
Place burgers on buns, top each with pizza sauce and cheese. Arrange lettuce and a slice of tomato on the other half of the bun. Garnish, if desired, with rings of grilled green pepper and red onion.