Heat oil in a large skillet over medium-high heat. Add green beans and crushed red pepper and cook, stirring often, until seared in spots, 2 to 3 minutes. Add water, cover, reduce heat to medium and cook, stirring occasionally, about 3 minutes for tender-crisp or 6 minutes for tender. Uncover, increase heat to medium-high, add stir-fry vegetables and black bean-garlic sauce. Cook, stirring often, until heated through and most of the liquid has evaporated, 1 to 2 minutes.

Ingredient Note: Black bean-garlic sauce: This savory, salty sauce used in Chinese cooking is made from fermented black beans, garlic and rice wine. Found in the Asian-food section of large supermarkets or at Asian markets. Use it in stir-fries and marinades for beef, chicken or tofu.