In a medium bowl, stir together lean ground pork, mushrooms, bread crumbs, and oregano. Shape mixture into 6 patties.
Preheat barbecue to high; reduce temperature to medium just before grilling.
Place patties on lightly greased grill; close barbecue cover and grill 5 to 7 minutes per side or until no longer pink inside. OR, fry in lightly greased skillet at medium-high heat until no longer pink inside.
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. Enjoy!