Sliced beef is stir-fried in a rich, nutty satay sauce with onions and bell peppers. High in protein and full of complex savory flavor, this dish is a quick family dinner with Southeast Asian-Chinese flair.
Slice the beef flank steak thinly against the grain and set aside.
Mix creamy peanut butter, soy sauce, oyster sauce, brown sugar, rice vinegar, minced garlic, minced fresh ginger, and water in a small bowl to make the satay sauce.
Heat 1 tablespoon vegetable oil in a wok or large skillet over high heat. Add sliced beef in a single layer and sear for 1-2 minutes until just browned; remove from pan.
Add remaining 1 tablespoon oil and stir-fry sliced onions and both bell peppers over medium-high heat for 2-3 minutes until just tender but still crisp.
Return the beef to the pan, pour in the satay sauce, and toss everything together. Stir-fry for another 2-3 minutes on medium heat until the sauce thickens and evenly coats the beef and vegetables.
Remove from heat promptly to preserve the beef’s tenderness. Serve hot.