This is a fast weeknight stir-fry built around thinly sliced beef sirloin, two bell peppers, and a short list of pantry staples. It comes together in 30 minutes, uses one pan, and produces real heat without a complicated sauce. If you have soy sauce, garlic, and something spicy in the fridge, you’re most of the way there.
The technique that matters
Two things determine whether this stir-fry is good or just okay. First, slice the beef as thin as you can — ideally under a quarter inch — and cut against the grain. Thick slices stay chewy no matter how long you cook them. Pop the sirloin in the freezer for 15 minutes before slicing if it keeps sliding around on the cutting board. Second, cook the beef in batches and don’t crowd the pan. A crowded wok steams the meat instead of searing it, and you lose the browning that gives the dish its depth. Each batch should take about 2 minutes over high heat. Both steps are quick, and skipping either one is where most home cooks run into trouble.
About the ingredients
- Beef sirloin: Flank steak or skirt steak work just as well and are often cheaper. Avoid stew beef — the chunks are too thick and the cut is wrong for fast, high-heat cooking.
- Chili paste: Sambal oelek is the most common option and easy to find. Sriracha works in a pinch but is thinner and sweeter, so start with less. Gochujang adds a fermented note and is a solid swap if that’s what’s in your fridge.
- Cornstarch: Don’t skip it. It’s what gives the beef that slightly glossy coating and helps the soy sauce cling. Arrowroot powder is a 1:1 substitute if needed.
- Bell peppers: Any color works. One pepper of any color plus a handful of whatever crunchy vegetable you have — snap peas, thinly sliced carrot, or broccoli florets — is a perfectly fine substitution.
- Sesame seeds: Skip the garnish — not worth the extra dish if you don’t already have them open. The scallions alone do the job.
Make-ahead notes
The beef can be sliced, tossed with soy sauce and cornstarch, and stored covered in the fridge for up to 8 hours before cooking — the marinade won’t hurt it over that window. Fully cooked leftovers keep well in an airtight container for up to 3 days. Reheat in a hot skillet with a splash of water or a few drops of soy sauce to loosen the sauce; the microwave works but softens the peppers considerably. This dish doesn’t freeze well — the bell peppers turn watery and the beef texture suffers — so plan to eat it within the week.
Mistakes to avoid
- Starting with cold beef straight from the fridge: Cold meat drops the pan temperature fast and you get steaming instead of searing. Let it sit out for 10 minutes while you prep everything else.
- Adding garlic and ginger too early: Both burn quickly at high heat. Add them after the peppers have had a few minutes in the pan, not at the start, and keep them moving.
- Using low heat because you’re nervous about burning: Stir-fry needs high heat. If the oil isn’t shimmering before the beef goes in, you won’t get any browning. Turn the burner up and stay at the stove.
- Skipping the rest step after removing the beef: The beef goes back into the wok at the end for 2-3 more minutes. If you skip setting it aside and just leave it in the whole time, it overcooks and toughens while the vegetables finish.
- Under-seasoning at the end: Chili paste varies a lot by brand in both heat and salt. Taste before serving and add a small splash of soy sauce if the sauce tastes flat — it usually just needs a little more salt to pull everything together.
Spicy Beef Stir-Fry
Equipment
- Wok or large frying pan
- Cutting board
- Chefs Knife
- Wooden spoon or spatula
- Mixing bowl
Ingredients
- 1 pound beef sirloin sliced thinly against the grain
- 2 tablespoons soy sauce preferably low-sodium
- 1 tablespoon cornstarch
- 3 tablespoons vegetable oil divided
- 1 medium red bell pepper sliced into strips
- 1 medium green bell pepper sliced into strips
- 3 cloves garlic minced
- 1 inch ginger grated
- 1 tablespoon chili paste adjust to taste
- 2 stalks scallions sliced, for garnish
- 1 tablespoon sesame seeds toasted, for garnish
Instructions
- In a mixing bowl, combine the beef slices, soy sauce, and cornstarch. Let it marinate for at least 10 minutes to tenderize the meat and infuse it with flavor.
- Heat 2 tablespoons of vegetable oil in a wok over medium-high heat. When the oil shimmers, add the beef in batches, sautéing until browned on all sides. Remove and set aside.
- In the same wok, add the remaining tablespoon of oil. Stir in the red and green bell peppers, sautéing until they start to caramelize and soften, about 3-4 minutes.
- Add the minced garlic and grated ginger to the wok, stirring for another minute until fragrant. Be careful not to burn the garlic.
- Return the beef to the wok along with the chili paste. Stir-fry everything together for another 2-3 minutes, ensuring the beef is cooked through and well coated with the spices.
- Remove from heat and garnish with sliced scallions and toasted sesame seeds before serving.
Notes
- For a smokier flavor, try using smoked chili paste.
- If you're sensitive to heat, reduce the amount of chili paste or substitute with sweet chili sauce.
- To make this recipe gluten-free, use tamari in place of soy sauce.
- Consider adding a splash of lime juice for an extra punch of citrus freshness at the end.
Nutrition
Frequently asked questions
Can I use a regular skillet instead of a wok?
Yes, a large heavy skillet works fine. A wok’s sloped sides make tossing easier, but a 12-inch stainless or cast iron pan over high heat will give you good browning as long as you don’t overcrowd it.
How spicy is this with 1 tablespoon of chili paste?
At 1 tablespoon it’s noticeable but not overwhelming for most people — call it a medium heat. If you’re cooking for kids or spice-sensitive eaters, start with a teaspoon and taste before adding more.
Can I use a different cut of beef to save money?
Flank steak and skirt steak are both cheaper than sirloin and work well here. The key is still slicing thin against the grain — with those cuts it matters even more because the muscle fibers are longer.
What can I serve this with besides rice?
Rice noodles are the most natural swap and cook in about 5 minutes. Ramen noodles, udon, or even plain spaghetti in a pinch will all absorb the sauce well.
My sauce looks dry by the time I add the beef back in — what happened?
The cornstarch coating on the beef absorbs liquid quickly at high heat. Add a tablespoon or two of water or low-sodium soy sauce when you return the beef to the wok and stir immediately to loosen things up.
Can I make this without fish sauce or oyster sauce?
This recipe doesn’t call for either, so you’re already set. If you’re adapting a version that does, a small extra splash of soy sauce plus a drop of Worcestershire covers most of the savory depth those ingredients provide.
What to cook next
- Spicy Korean Rice Cakes
- Quick Ginger Scallion Wontons
- Sizzling Skillet Steak Fajitas
- Quick Korean Bibimbap Bowls