Crockpot Mongolian Beef (Better Than Takeout)

Tender strips of beef slow-cooked in a sweet soy and ginger sauce until they almost melt. It’s one of those set-it-and-forget-it meals that tastes like you spent hours fussing at the stove.

The sauce turns glossy and thick right in the crock, clinging to every piece of meat. Serve it over rice with a pile of fresh green onions, and you have a dinner that beats a delivery carton hands down.

What Makes This One So Good

The flank steak becomes silky after a long, gentle cook, while the brown sugar and soy sauce reduce into a sticky glaze with deep savory notes. There is no cornstarch slurry at the end—the beef’s initial coating thickens the sauce naturally as it cooks.

I love that I can toss everything in on a busy afternoon and come back to a finished meal. Even the pickiest eaters go quiet and just keep eating.

Ingredients

• 2 lbs flank steak, sliced ¼ inch thick against the grain: look for a piece with even thickness so it cooks uniformly
• ¼ cup cornstarch: this coats the beef and will thicken the sauce
• ½ cup soy sauce: low-sodium gives you control over saltiness
• ⅓ cup packed brown sugar: light or dark both work; dark adds a little molasses depth
• ½ cup water: creates the sauce volume
• 4 cloves garlic, minced: fresh is best
• 1 tsp grated fresh ginger: or ½ tsp dried ginger
• 2 tbsp vegetable oil: for searing the beef
• 4 green onions, sliced on the diagonal: use both white and green parts
• 1 tbsp sesame seeds: for a little crunch at the end

Variations / Substitutions

• Swap the protein: Thinly sliced chuck steak or even boneless chicken thighs can stand in for the flank steak. Chicken will cook faster, so check after 2 hours on high.
• Adjust the sweetness: If you prefer a less sweet sauce, cut the brown sugar to ¼ cup and add a splash of rice vinegar at the end to brighten things up.
• Add some heat: Stir in 1 tsp of sriracha or chili garlic sauce with the soy mixture for a spicy kick.
• Go gluten-free: Use tamari instead of soy sauce and double-check your cornstarch is gluten-free.

How to Make Crockpot Mongolian Beef

Step 1: Sear the Beef

Drop the sliced flank steak into a large bowl, sprinkle the ¼ cup cornstarch over it, and toss with your hands until every piece is well coated. Shake off any excess. Heat the 2 tbsp vegetable oil in a large skillet over high heat until it shimmers, about 1 minute. Working in batches so you don’t crowd the pan, lay the beef in a single layer and sear for 2 minutes per side, just until browned. You’re not cooking it through, just giving it a crust.

The beef will look pale and dusty from the cornstarch before it hits the pan, then turn a deep brown as it sears. A little sticking is normal; that’s the starch doing its job.

Step 2: Build the Sauce

While the beef is searing, whisk the ½ cup soy sauce, ⅓ cup brown sugar, ½ cup water, minced garlic, and grated ginger together in a bowl until the sugar dissolves. Taste it. It should be salty-sweet with a clear ginger note. Pour this mixture directly into your slow cooker.

Do not wash the skillet yet, those browned bits are flavor. You’ll use them in a moment.

Step 3: Slow Cook the Beef

Transfer the seared beef to the slow cooker, scraping any bits from the skillet into the pot. Stir everything together so the beef is coated in sauce. Put the lid on and cook on low for 6 hours or on high for 3 hours. The meat should be fork-tender and the sauce will look slightly thickened and glossy.

About halfway through, give it a gentle stir if you’re around; if not, it will still cook evenly. The long, low heat breaks down the connective tissue in flank steak, turning what can be a chewy cut into spoon-tender strips.

Step 4: Finish and Serve

Once the beef is done, stir in most of the sliced green onions, reserving a handful for garnish. Scoop the beef and sauce right over a mound of steamed white rice, then scatter the remaining green onions and the sesame seeds on top. The sauce should coat the rice like syrup, and the green onion adds a crisp, fresh bite against all that richness. Serve while it’s piping hot.

Tips for the Best Crockpot Mongolian Beef

• Slice against the grain: Look for the lines of muscle in the flank steak and cut perpendicular to them. This shortens the fibers and makes the meat more tender after cooking.
• Don’t skip the sear: Browning the beef adds a deep, savory note that slow cooking alone can’t create. Even 2 minutes per side makes a difference.
• Make it saucy for noodles: If you want extra sauce to toss with cooked lo mein or rice noodles, double the soy sauce, brown sugar, and water amounts.
• Watch the salt: Different soy sauces vary in saltiness. If you only have regular soy sauce, skip any extra salt in the recipe and taste before serving.

Slow cooker times for tender beef:

Storing Leftovers

Cool the beef and sauce completely, then transfer to an airtight container. It will keep in the refrigerator for up to 4 days and the flavor actually gets better overnight.

Reheat gently in a saucepan over low heat with a splash of water to loosen the sauce, or microwave portions in 1-minute bursts, stirring between each. You can also serve it cold over a crisp salad, if you’re into that kind of thing.

What to Serve With Crockpot Mongolian Beef

A simple bowl of steamed jasmine rice is the classic partner—the fluffy grains soak up the sticky sauce beautifully. For a vegetable, steamed broccoli or snap peas tossed with sesame oil keep the meal light. If you want something that feels a little more takeout-inspired, pan-fried noodles with a drizzle of extra soy sauce work really well.

Frequently Asked Questions

Can I use a different cut of beef?

Yes. Chuck steak or flat iron steak will both work, though they have more marbling and turn out even richer. Just slice them thin against the grain like you would with flank.

My sauce turned out runny. What went wrong?

This usually happens if the beef wasn’t coated evenly in cornstarch or the slow cooker lid was lifted too often. Place the leftovers in a saucepan over medium heat, bring to a simmer, and cook until it thickens up, about 5 minutes.

Can I make this ahead of time?

Absolutely. Cook it fully, cool, and refrigerate. The next day, reheat on the stovetop and add the fresh green onions and sesame seeds just before serving.

Is there a way to cut the sweetness?

Reduce the brown sugar to 2 tablespoons and add 1 tablespoon of rice vinegar to the sauce before cooking. The vinegar balances the sweetness without changing the texture.

Crockpot Mongolian Beef Recipe

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Prep Time 15 minutes mins

Cook Time 6 hours hrs

Total Time 6 hours hrs 15 minutes mins

Servings: 4 servings

Calories: 392

Ingredients Method Notes

Ingredients

  

• 2 lbs flank steak, sliced ¼ inch thick against the grain
• ¼ cup cornstarch
• ½ cup soy sauce
• ⅓ cup packed brown sugar
• ½ cup water
• 4 cloves garlic, minced
• 1 tsp grated fresh ginger
• 2 tbsp vegetable oil
• 4 green onions, sliced on the diagonal
• 1 tbsp sesame seeds

Method

 

1. Toss the sliced flank steak with cornstarch until coated. Shake off excess. Sear in batches in hot oil over high heat for 2 minutes per side.
2. Whisk together soy sauce, brown sugar, water, garlic, and ginger. Pour into the slow cooker.
3. Add the seared beef to the slow cooker, stir to coat. Cook on low for 6 hours or high for 3 hours.
4. Stir in most of the green onions. Serve over rice, topped with remaining green onions and sesame seeds.

Notes

This dish is best on the day it’s made, but holds up well in the fridge. If you want a thicker sauce, let it sit on the warm setting with the lid off for 10 minutes before serving.