Preheat your oven to 350°F (175°C) to prepare for baking the beans evenly.
In a large pot or deep skillet over medium heat, combine the drained kidney beans, pinto beans, and petite diced tomatoes with their juices. Stir to mix well.
Add the pizza sauce, dried oregano, and freshly ground black pepper to the bean mixture. Stir thoroughly to blend the flavors.
Fold in about half of the mini pepperoni into the bean mixture to distribute the flavor evenly.
Transfer the bean and pepperoni mixture into an oven-safe baking dish, spreading it evenly.
Sprinkle the shredded mozzarella cheese generously over the top, then arrange the remaining mini pepperoni on the cheese for a classic pizza look.
Bake in the preheated oven for 25-30 minutes until the cheese is melted, bubbly, and slightly browned at the edges.
Remove from oven, let cool for a few minutes, then garnish with finely minced fresh parsley before serving hot.