Place beef round steak in a 3-quart slow cooker.

In a small bowl, combine diced tomatoes, chopped onion, minced garlic, dried oregano, chili powder, ground cumin, salt, and pepper.

Pour the tomato mixture over the steak in the slow cooker.

Cover the slow cooker and cook on LOW for 8-9 hours, or until the meat is very tender.

Remove the cooked beef from the slow cooker and set aside.

Add the rinsed and drained pinto beans to the tomato mixture remaining in the slow cooker.

Cover and cook on HIGH for 30 minutes, or until the beans are heated through.

Once the beef is cool enough to handle, slice or shred it into smaller pieces.

In individual serving bowls, layer hot cooked rice, sliced/shredded beef, and the pinto bean mixture.

Top each bowl with shredded cheddar cheese, sliced ripe olives, thinly sliced green onions, and guacamole.