Add the sliced onion and bell peppers to the bottom of a 4-6 quart slow cooker. Place the beef chuck roast on top of the vegetables.

In a small bowl, whisk together the Worcestershire sauce, beef stock, minced garlic, dried oregano, salt, and black pepper. Pour this mixture evenly over the meat and vegetables in the slow cooker.

Cover the slow cooker and cook on LOW for 8 hours, or until the beef is tender and easily shreds. Stir to break up the meat before serving.

Serve the slow cooker pepper steak over cooked rice, pasta, or on hoagie rolls as sandwiches.