In 10-inch skillet heat oil; add onions, red peppers, garlic, and ginger and saute over medium heat until vegetables are tender-crisp, about 4 minutes.
In small bowl combine water, hoisin sauce, and cornstarch, stirring to dissolve cornstarch; add to vegetable mixture, along with broth mix and, stirring constantly, bring to a boil.
Continue stirring and cook until thickened; add broccoli and stir to combine.
Reduce heat to lowest possible setting, just hot enough to keep mixture warm while beef is cooking.
On rack in broiling pan broil beef for 4 to 5 minutes on each side, depending on thickness of meat; remove from rack and slice across the grain into thin strips.
Transfer vegetable mixture to serving platter and top with beef.