That moment when you open a takeout container and find tender beef coated in a glossy, sweet-savory sauce? You can get remarkably close to that experience at home—without standing over a wok.
This crockpot Mongolian beef combines thinly sliced flank steak or sirloin with a rich sauce made from low-sodium soy sauce, brown sugar, garlic, ginger, and a splash of rice vinegar. The slow cooker does most of the work, while a quick cornstarch slurry at the end thickens the sauce and makes it glossy.
The trick is not cooking the beef all day. Unlike a chuck roast, lean cuts such as flank steak and sirloin don’t necessarily become more tender the longer they cook. A shorter cooking window helps keep the thin strips from drying out and becoming chewy.
Serve the finished beef over steamed rice with broccoli or another favorite vegetable for an easy weeknight dinner with serious takeout appeal.
Why You’ll Love This Crockpot Mongolian Beef
- Big takeout-style flavor. Soy sauce, brown sugar, garlic, ginger, sesame oil, and rice vinegar create a balanced sweet-savory sauce.
- Minimal hands-on cooking. Once the beef and sauce are in the slow cooker, most of the work is done.
- A shorter cooking time. The recipe is designed specifically for thin strips of flank steak or sirloin rather than tough roast cuts.
- Glossy sauce. A finishing cornstarch slurry helps the sauce cling to the beef and rice.
- Easy to customize. Add red pepper flakes for heat or serve the beef with broccoli for a more complete meal.
The Secret to Better Slow Cooker Beef
The biggest mistake with this recipe would be assuming that more cooking time automatically means more tender beef.
Flank steak and top sirloin are relatively lean cuts. They’re excellent when sliced thinly against the grain, but they aren’t the same as chuck roast, which becomes tender after hours of cooking as its connective tissue breaks down.
That’s why this recipe uses a shorter slow-cooker window.
For the best texture:
- Chill the steak in the freezer for about 20–30 minutes before slicing. Slightly firm meat cuts more easily.
- Slice against the grain into consistent strips about ¼ inch thick.
- Start checking the beef at the earliest suggested cooking time.
- Don’t keep cooking for hours just because the beef hasn’t reached pot-roast texture. Lean steak can become tougher with prolonged cooking.
- If your slow cooker runs hotter or cooler than average, use the beef’s texture—not just the clock—as your guide.
Tips for the Best Crockpot Mongolian Beef
Slice the steak against the grain.
This is one of the most important steps for getting a pleasant texture. Look for the direction of the muscle fibers and cut across them, not parallel to them.
If the steak is difficult to slice thinly, partially freezing it first makes the job much easier.
Don’t overcook lean beef.
The short cooking time is intentional. Flank steak and sirloin don’t need the all-day cooking schedule used for tougher cuts such as chuck roast.
Start checking the beef at the earliest suggested cooking time.
Don’t expect crispy beef from the slow cooker.
Traditional restaurant versions of Mongolian beef may use fried or seared beef. This slow-cooker version has a different texture: the beef is tender and coated in a thick, glossy sauce rather than crisp.
For more browning, use the optional skillet step before adding the beef to the slow cooker.
Use low-sodium soy sauce.
Because the recipe uses a generous amount of soy sauce, low-sodium soy sauce gives you more control over the final salt level.
If you’re using regular soy sauce, you may want to replace some of it with additional water or unsalted beef broth.
Give the slurry time to work.
Cornstarch thickens best when mixed with cold water first. Stir it in thoroughly, then cook on HIGH for about 15 minutes to finish thickening the sauce.
Crockpot Mongolian Beef Recipe
Thin strips of flank steak or sirloin simmer in a sweet-savory soy, garlic, and ginger sauce, then get finished with a quick cornstarch slurry for a glossy coating.
Ingredients
For the Beef
- 1½ pounds flank steak or top sirloin
- ¼ cup cornstarch
- 1 tablespoon neutral cooking oil, such as avocado or canola, optional for browning
For the Mongolian Beef Sauce
- ½ cup low-sodium soy sauce
- ½ cup water or low-sodium beef broth
- ⅓ cup packed dark brown sugar
- 1 tablespoon rice vinegar
- 4 garlic cloves, minced
- 1 tablespoon fresh ginger, finely grated
- 1 teaspoon toasted sesame oil
- ¼ to ½ teaspoon red pepper flakes, optional
For Thickening and Serving
- 2 tablespoons cornstarch
- 2 tablespoons cold water
- 4 green onions, thinly sliced, with whites and green tops separated
- 1 tablespoon toasted sesame seeds
- Cooked white or brown rice, for serving
Instructions
- Place the steak in the freezer for about 20–30 minutes to firm it slightly, then slice it against the grain into thin, even strips about ¼ inch thick. Pat dry if needed.
- Place the sliced beef in a large bowl and toss with ¼ cup cornstarch until every piece is lightly and evenly coated so the sauce clings and turns silky.
- In a medium bowl, whisk together the soy sauce, water or broth, brown sugar, rice vinegar, garlic, ginger, sesame oil, and red pepper flakes until the sugar is mostly dissolved.
- (Optional) For deeper flavor, heat the neutral oil in a large skillet over medium-high heat. Working in batches, quickly brown the beef for about 1 minute per side without cooking it through, then transfer to the slow cooker. (Skipping this step still produces a delicious dish.
- Transfer the beef to a 6-quart slow cooker, pour over the sauce, add the white parts of the green onions, and stir gently to combine.
- Cover and cook on LOW for about 3 hours or on HIGH for 1½ to 2 hours. Do not overcook lean cuts; check toward the lower end of the range to keep the beef tender.
- Whisk 2 tablespoons cornstarch with 2 tablespoons cold water in a small bowl until completely smooth, then stir the slurry directly into the slow cooker. Cover and cook on HIGH for about 15 minutes until the sauce thickens into a glossy, takeout-style coating.
- Stir in half of the green onion tops, then spoon the beef over hot rice and garnish with the remaining green onions and toasted sesame seeds.
Notes
- Slicing the steak while partially frozen makes it infinitely easier to get those razor-thin, restaurant-quality strips.
- Let the cornstarch-coated beef sit for 5 minutes before adding it to the liquid so the starch securely adheres to the meat rather than clumping in the sauce.
Easy Variations
Crockpot Mongolian Beef and Broccoli
For an easy vegetable addition, use 3–4 cups broccoli florets.
For the best texture, steam the broccoli separately and serve it alongside the beef. You can also add the florets to the slow cooker during the final 20–30 minutes, although they will be softer.
Spicy Mongolian Beef
Increase the red pepper flakes to 1 teaspoon for more heat.
For a different kind of spice, add 1 tablespoon sriracha to the sauce before cooking.
Lighter Mongolian Beef
For a lighter version, reduce the brown sugar to ¼ cup and serve the beef with extra steamed vegetables.
Keep in mind that substitutions such as coconut aminos can change the flavor and salt level of the finished sauce, so taste and adjust rather than assuming a direct swap will taste identical.
Ground Beef Mongolian Beef
For a much faster dinner, brown 1½ pounds ground beef in a large skillet and drain excess fat.
Add the same sauce ingredients and simmer for about 10–15 minutes, stirring occasionally, until the sauce thickens.
This version has a completely different texture from sliced-beef Mongolian beef, but it works well for busy weeknights.
Chuck Roast Mongolian Beef
Want to use chuck roast instead? Don’t use the main recipe’s short cooking time.
Chuck roast contains more connective tissue and benefits from a longer cooking period. Cut about 1½ pounds chuck roast into bite-size strips or chunks and add it to the slow cooker with the sauce ingredients.
Cook on LOW for about 6–7 hours, or until the beef is fork-tender. Mix the cornstarch slurry separately and add it during the final 15–20 minutes to thicken the sauce.
Because this version uses a tougher cut, it’s more forgiving if dinner gets delayed.
Mongolian Beef Ramen
Skip the rice and serve the finished beef over cooked ramen noodles.
Use plain ramen noodles and discard the seasoning packet. Toss the noodles with some of the finished sauce before topping them with the beef and green onions.
Can You Make Crockpot Mongolian Beef Ahead?
Yes. You can prepare the beef and sauce ahead of time and refrigerate them separately until you’re ready to cook.
For freezer meal prep, combine the raw sliced beef and sauce ingredients in a freezer-safe bag, but leave out the cornstarch coating.
Freeze for up to 3 months. Thaw overnight in the refrigerator, then toss the beef with the cornstarch immediately before transferring it to the slow cooker.
Keeping the cornstarch out of the freezer bag prevents the coating from becoming clumpy or breaking down during freezing and thawing.
What to Serve With Mongolian Beef
The easiest pairing is steamed rice, which soaks up all that extra sauce.
For a more balanced dinner, add a vegetable such as:
- Steamed broccoli
- Roasted green beans
- Steamed snap peas
- Stir-fried bell peppers
- Edamame
You can also serve the beef over noodles instead of rice or tuck it into lettuce cups for a lighter meal.
Storage and Reheating
Store leftover Mongolian beef in an airtight container in the refrigerator for up to 4 days.
Reheat gently in the microwave or in a skillet over medium-low heat. If the sauce has become very thick, add a splash of water or beef broth while reheating.
You can also freeze the cooked beef for up to 3 months. Let it cool completely before transferring it to a freezer-safe container. Thaw overnight in the refrigerator and reheat gently.
Frequently Asked Questions
Is crockpot Mongolian beef supposed to be crispy?
No. This slow-cooker version produces beef coated in a thick, glossy sauce rather than the crisp exterior you may get from deep-fried restaurant versions.
If you want more browned flavor, use the optional skillet-browning step before slow cooking.
What is the best cut of beef for crockpot Mongolian beef?
Flank steak is an excellent choice because it slices easily and works well with the recipe’s shorter cooking time.
Top sirloin also works well. You can use strip steak, although it is generally more expensive.
Chuck roast and stew meat are better suited to longer cooking and should not be substituted into the main recipe with the same 3-hour cooking time.
Why did my Mongolian beef turn chewy?
The most likely causes are overcooking, slicing the beef incorrectly, or cutting the pieces too thick.
Slice the steak thinly against the grain, and begin checking it at the earliest suggested cooking time. Remember that lean beef doesn’t necessarily become more tender the longer it stays in the slow cooker.
Why is my sauce not thick enough?
First, mix the cornstarch with cold water until smooth before adding it to the slow cooker.
Then cook the beef on HIGH for about 15 minutes after adding the slurry. If the sauce remains thin, remove the lid and cook for a few more minutes to let some moisture evaporate.
Can I make this crockpot Mongolian beef with broccoli?
Yes. For the best texture, steam the broccoli separately and serve it with the beef.
If you prefer a one-pot meal, add broccoli during the final 20–30 minutes of cooking. It will be softer than steamed broccoli.
Can I freeze crockpot Mongolian beef?
Yes. For a freezer meal, freeze the raw beef and sauce together, but add the cornstarch only after the beef has thawed.
You can also freeze cooked leftovers for up to 3 months.
Can I use regular soy sauce instead of low-sodium?
Yes, but the finished dish will be saltier. Because the sauce already contains a substantial amount of soy sauce, low-sodium soy sauce gives you better control over the final flavor.
Can I double the recipe?
Yes, but use a larger slow cooker—ideally 7 or 8 quarts—and avoid filling the cooker beyond its recommended capacity.
Because a larger batch can affect how quickly the slow cooker heats, don’t rely solely on the original timing. Check the beef for doneness before moving on to the thickening step.
Final Thoughts
This crockpot Mongolian beef gives you the part everyone loves about takeout—the glossy sauce, garlicky aroma, sweet-savory flavor, and tender slices of beef—without requiring you to stand over the stove.
The key is resisting the temptation to cook the beef all day. Slice it thinly against the grain, start checking it early, and finish the sauce with a quick cornstarch slurry.
Serve it over rice with broccoli, add a little heat if you like, and you have a comforting dinner that’s easy enough for a weeknight but satisfying enough to make you forget about ordering takeout.
