Pepperoni Pizza Burgers

1 pound lean ground beef
15 ounces pizza sauce — canned
1 teaspoon dried oregano
1/2 onion
1/2 green bell pepper
1 ounce pepperoni slices
1/2 cup mozzarella cheese — shredded
1/2 cup sliced mushrooms
6 hamburger buns — split
In a skillet, brown ground beef; drain.
Stir in pizza sauce and oregano.
In a food processor, chop onion, pepper, pepperoni; add to beef mixture.
Simmer 20-25 minutes.
Spoon onto buns, top with cheese and mushrooms.
Serve immediately.