In a large bowl, combine the sliced steak and shrimp. Season with salt and pepper. In a small bowl, mix the soy sauce, oyster sauce, cornstarch, water, and sesame oil to create the stir-fry sauce.
Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Add the steak and cook for about 2-3 minutes until browned. Remove the steak from the skillet and set aside.
In the same skillet, add the remaining tablespoon of oil. Add the garlic and ginger, sautéing for about 30 seconds until fragrant.
Add the sliced bell peppers and snap peas to the skillet. Stir-fry for about 3-4 minutes until the vegetables are tender-crisp.
Return the cooked steak to the skillet along with the shrimp. Pour the stir-fry sauce over the mixture and cook for an additional 2-3 minutes until the shrimp are pink and cooked through.
Serve immediately over cooked rice or noodles.