Slice the beef into thin strips against the grain.
Optional: lightly brown beef in a skillet with olive oil.
Place sliced beef into the crockpot.
Add sliced onions and bell peppers over the beef.
Add minced garlic to the crockpot.
In a bowl, whisk beef broth, soy sauce, brown sugar, black pepper, and ginger powder.
Pour the sauce mixture over the beef and vegetables.
Cover and cook on low for 6 hours or until beef is tender.
Mix cornstarch with water and stir into the crockpot during the last 30 minutes.
Cook until sauce thickens, then serve hot.