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Slow Cooker Mongolian Beef

This Slow Cooker Mongolian Beef is a tender, flavorful dinner featuring thinly sliced beef simmered in a rich sweet-and-savory sauce made with soy sauce, brown sugar, garlic, ginger, and sesame oil. The slow cooker makes the beef wonderfully tender while the sauce develops a glossy, flavorful finish. Serve it over steamed rice with green onions and sesame seeds for an easy restaurant-style meal at home.

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Prep Time 15 minutes
Cook Time 4 hours
Total Time 4 hours 15 minutes
Servings: 6
Ingredients Method Notes

Ingredients
  

  • For the Beef
  • 2 pounds flank steak or sirloin steak thinly sliced
  • ¼ cup cornstarch
  • ½ teaspoon salt
  • ¼ teaspoon black pepper
  • 1 tablespoon vegetable oil
  • For the Sauce
  • ¾ cup low-sodium soy sauce
  • ½ cup beef broth
  • ½ cup packed brown sugar
  • 4 cloves garlic minced
  • 1 tablespoon fresh ginger grated
  • 1 tablespoon rice vinegar
  • 1 teaspoon toasted sesame oil
  • ½ teaspoon red pepper flakes optional
  • For Serving
  • 4 –6 cups cooked white or brown rice
  • 3 green onions thinly sliced
  • 1 tablespoon sesame seeds
  • Steamed broccoli optional
  • Sliced carrots optional

Method
 

  1. Slice the beef thinly against the grain for a more tender texture.
  2. Place the beef in a large bowl and sprinkle with cornstarch, salt, and black pepper. Toss until evenly coated.
  3. Heat vegetable oil in a large skillet over medium-high heat.
  4. Working in batches, sear the beef for about 1–2 minutes per side until lightly browned. This step is optional but adds extra flavor.
  5. Transfer the beef to the slow cooker.
  6. In a bowl, whisk together soy sauce, beef broth, brown sugar, garlic, ginger, rice vinegar, sesame oil, and red pepper flakes.
  7. Pour the sauce over the beef and stir gently to coat.
  8. Cover and cook on LOW for 4–6 hours or HIGH for 2–3 hours, until the beef is tender.
  9. Check the sauce near the end of cooking. If it needs additional thickening, mix 1 tablespoon cornstarch with 2 tablespoons cold water and stir it into the slow cooker.
  10. Cook for another 15–20 minutes until the sauce thickens.
  11. Garnish with sliced green onions and sesame seeds.
  12. Serve hot over cooked rice with steamed vegetables.

Notes

  • Slice the beef against the grain for the best texture.
  • Flank steak or sirloin works particularly well.
  • Searing the beef is optional but adds a deeper flavor.
  • Use low-sodium soy sauce to better control the saltiness.
  • Adjust the brown sugar according to how sweet you like the sauce.
  • Add red pepper flakes for a little heat.
  • Add broccoli or bell peppers during the final 30 minutes to help prevent them from becoming too soft.
  • Serve with white rice, brown rice, or noodles.
  • For a thicker sauce, use a cornstarch slurry near the end of cooking.