Slow Cooker Mongolian Beef

This Slow Cooker Mongolian Beef has tender slices of beef cooked in a rich, sweet and savory sauce with soy sauce, brown sugar, garlic, and ginger. A quick sear gives the beef extra flavor before everything goes into the slow cooker, where the sauce thickens and coats the beef beautifully.

Serve it over steamed rice or noodles and finish with green onions for an easy takeout-style dinner made right at home

I first shared this Mongolian beef recipe back in 2017, and it has been a reader favorite ever since. I still like to sear the beef before adding it to the slow cooker. It takes a few extra minutes, but those browned edges add so much more flavor to the finished dish.

Why You’ll Love This Recipe

• Tender, flavorful beef – Thin slices of flank steak cook in a rich sweet and savory sauce.
• Better flavor from searing – Browning the beef first adds another layer of flavor before it goes into the slow cooker.
• Simple sauce – Soy sauce, brown sugar, garlic, ginger, and tomato paste make a glossy sauce with plenty of flavor.
• Perfect with rice or noodles – An easy dinner that needs little more than a simple side.

Ingredients and Substitutions

• Beef – Flank steak works best here. Slice it thinly against the grain so it stays tender during cooking. Sirloin can also be used.
• Flour – Lightly coats the beef, helps it brown, and thickens the sauce as it cooks.
• Onion – Adds sweetness and flavor to the sauce.
• Garlic and ginger – Use fresh for the best flavor.
• Soy sauce – Gives the sauce its salty, savory base. Low-sodium soy sauce works well if you prefer more control over the salt.
• Brown sugar – Gives Mongolian beef its characteristic sweet-savory flavor and helps balance the soy sauce.
• Beef broth – Adds enough liquid for slow cooking without making the sauce watery.
• Tomato paste – Adds richness, color, and body to the sauce. We keep this because it is part of your original recipe/video.
• Red pepper flakes – Add a little heat; use more or less to taste.
• Green onions – Add freshness and are best added toward the end.
• Sesame seeds – Optional, for garnish.

Step-by-Step – Slow Cooker Mongolian Beef

Prepare the beef – Slice the flank steak thinly against the grain. Pat it dry, then season lightly with black pepper.

Coat with flour – Add the flour to the beef and toss until the slices are lightly coated. Shake off any excess.

Sear the beef – Heat the oil in a large skillet over medium-high heat. Sear the beef in batches for about 1–2 minutes per side, just until browned. Do not cook it through. Transfer to the slow cooker.

Sauté the aromatics – In the same skillet, add the onion and cook for 2–3 minutes. Add the garlic and ginger and cook for another 30 seconds.

Make the sauce – Add the soy sauce, beef broth, brown sugar, tomato paste, red pepper flakes, and black pepper. Stir well, scraping up any browned bits from the bottom of the pan.

Combine – Pour the onion and sauce mixture over the beef in the slow cooker. Stir gently to coat everything. The liquid does not need to completely cover the beef.

Slow cook – Cover and cook on LOW for about 2½ to 3 hours, or until the flank steak is tender. Avoid cooking much longer, as thinly sliced flank steak does not need the same long cooking time as chuck.

Finish and serve – Stir in most of the sliced green onions. Garnish with the remaining green onions and sesame seeds, if using. Serve hot over steamed rice or noodles.

Can I make this on the Stovetop?

• Use a Dutch oven or a heavy-bottom pot, and follow the steps above: sear, sauté, and combine. Then, cover and cook on low heat for 2 to 3 hours.

Make Ahead and Storage

• Make ahead – Slice the beef and prepare the sauce up to a day ahead. Store them separately in the refrigerator, then assemble and cook when ready.
• Refrigerator – Store leftover Mongolian beef with its sauce in an airtight container for 3 to 4 days.
• Freezer – Freeze the cooked beef and sauce in an airtight container for up to 2 months. Thaw overnight in the refrigerator.
• Reheat – Reheat gently in a skillet over medium-low heat or in the microwave until hot. Add a splash of beef broth or water if the sauce has become too thick.

Veena Azmanov

Slow Cooker Mongolian Beef

5 from 29 votes

Tender slices of flank steak are lightly coated in flour, quickly seared, then slow-cooked with onion, garlic, ginger, soy sauce, brown sugar, and tomato paste. The result is tender beef in a rich, sweet and savory Mongolian-style sauce that’s perfect served over rice or noodles.

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Prep Time 10 minutes mins

Cook Time 6 hours hrs

Total Time 6 hours hrs 10 minutes mins

Servings: 6 servings

Course: Main Course

Cuisine: Mongolian

Calories: 362

Video

Ingredients

 

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• 1 kg (2 lbs) Flank steak thinly sliced against the grain
• 4 tbsp (¼ cup) All-purpose flour
• 2 tbsp Cooking oil plus more if needed
• 1 med Onion thinly sliced
• 4 large Garlic cloves minced
• 1 tbsp Fresh ginger grated
• 120 ml (½ cup) Low-sodium soy sauce
• 120 ml (½ cup) Beef broth
• 65 g (⅓ cup) Brown sugar
• 1 tbsp Tomato paste
• ½ tsp Red pepper flakes or to taste
• ½ tsp Black pepper
• 3 – 4 Green onions sliced
• 1 tbsp Sesame seeds optional for garnish

Method

 

1. Prepare the beef – Pat the flank steak dry and slice it thinly against the grain. Add the flour and toss until the beef is lightly coated. Shake off any excess.
   1 kg Flank steak, 4 tbsp All-purpose flour
2. Sear – Heat the oil in a large skillet over medium-high heat. Sear the beef in batches for 1–2 minutes per side, just until browned. Do not cook it through. Transfer the beef to the slow cooker.
   2 tbsp Cooking oil
3. Sauté – In the same skillet, add the onion and cook for 2–3 minutes. Add a little more oil if needed. Add the garlic and ginger and cook for 30 seconds.
   1 med Onion, 4 large Garlic cloves, 1 tbsp Fresh ginger
4. Make the sauce – Add the soy sauce, beef broth, brown sugar, tomato paste, red pepper flakes, and black pepper. Stir well, scraping up the browned bits from the bottom of the skillet.
   120 ml Low-sodium soy sauce, 120 ml Beef broth, 65 g Brown sugar, 1 tbsp Tomato paste, ½ tsp Red pepper flakes, ½ tsp Black pepper
5. Slow cook – Pour the sauce and onions over the beef. Stir gently to coat. Cover and cook on LOW for 2½ to 3 hours, or until the beef is tender.
   3 – 4 Green onions
6. Finish – Stir in most of the green onions. Garnish with the remaining green onions and sesame seeds, if using.
7. Serve – Serve hot over steamed rice or noodles.
   1 tbsp Sesame seeds

Notes

• Slice the flank steak against the grain for the most tender result.
• Sear the beef in batches so it browns rather than steams.
• The sauce does not need to cover the beef completely in the slow cooker.
• Start checking the beef at about 2½ hours.
• Thinly sliced flank steak does not need an all-day slow cook.
• Soy sauce is already salty, so taste before adding any additional salt.
• Leftovers keep in an airtight container in the refrigerator for 3 to 4 days.

Equipment you will need

Slow cooker

Cast-Iron Skillet

Mixing Bowl

Nutrition

Serving: 73g | Calories: 362kcal | Carbohydrates: 20g | Protein: 39g | Fat: 13g | Saturated Fat: 4g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 6g | Cholesterol: 100mg | Sodium: 972mg | Potassium: 781mg | Fiber: 2g | Sugar: 12g | Vitamin A: 152IU | Vitamin C: 4mg | Calcium: 81mg | Iron: 4mg

Tried this recipe?

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Tips for Success

• Slice against the grain – This shortens the muscle fibers and keeps the flank steak tender.
• Pat the beef dry before flouring – The flour will coat it more evenly and the beef will brown better.
• Sear in batches – Crowding the skillet causes the beef to steam instead of brown.
• Don’t cook the beef too long – Flank steak is thin and cooks much faster than chuck. Start checking it around the 2½-hour mark on LOW.
• Don’t worry if the sauce doesn’t cover the beef – The beef and onions release additional moisture as they cook.
• Taste before adding salt – Soy sauce already brings plenty of salt, so extra salt may not be necessary.

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Hi, I’m Veena

I’m the recipe developer, baker, and food photographer behind Veena Azmanov Kitchen.
I’ve spent years developing and testing recipes, from everyday meals and homemade breads to cakes and desserts.
I share the practical tips and little details I’ve learned along the way so you can get great results in your own kitchen.

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