In a large mixing bowl, combine the sliced beef, soy sauce, Worcestershire sauce, cornstarch, ground black pepper, and salt. Toss until the beef is well coated and let it marinate for about 10 minutes.
Heat the olive oil in a skillet over medium-high heat. Sear the marinated beef strips in batches until browned (around 3-4 minutes per batch). This step adds flavor but is optional if you want to skip it for a quicker prep.
Transfer the seared beef to the crock pot. Add the sliced bell peppers, sliced onion, minced garlic, and beef broth on top of the beef.
Stir the ingredients gently to combine, making sure the beef and vegetables are evenly distributed in the broth.
Cover the crock pot with the lid and cook on low heat for 6 hours or on high heat for 3 hours.
Once cooking time is complete, taste and adjust seasoning if necessary before serving.