Prepare the sauce by combining soy sauce, rice vinegar, and sesame oil in a bowl.
Heat a large skillet over medium-high heat and add ground beef.
Add garlic and ginger, cooking until fragrant, about 1-2 minutes.
Incorporate diced bell pepper and shredded carrots, stirring until softened, 3-4 minutes.
Pour the sauce over the beef and vegetables, stirring to coat.
Simmer for about 2-3 minutes, allowing the sauce to thicken. Taste and adjust seasoning as needed.
Stir in sliced green onions just before serving.
Serve the beef mixture in lettuce leaves and garnish with additional green onions if desired.