In a small bowl, whisk together the soy sauce, oyster sauce, and cornstarch until smooth. Set aside.

Slice beef across the grain and marinate briefly in a shallow dish with a tablespoon of soy sauce.

Chop all vegetables and store them in a single container for efficiency.

Measure sauces and cornstarch into a bowl to avoid scrambling while cooking.

Heat the vegetable oil in a large skillet or wok over medium-high heat until shimmering.

Add the marinated beef in a single layer and cook, stirring occasionally, for 2-3 minutes until browned. Remove from the pan if needed.

Add minced garlic and ginger to the skillet and stir-fry for about 30 seconds until fragrant.

Toss in mixed vegetables and stir-fry on high heat for 3-4 minutes until tender-crisp.

Return the beef to the pan and pour the sauce mixture over the ingredients, tossing to coat. Cook for an additional minute until the sauce thickens.

Serve the stir-fry immediately over cooked rice or noodles.