Whisk together soy sauce, vinegar, sugar and chili paste; set aside.
Heat oil in a large nonstick skillet over medium-high heat. Add beef; cook for 2 minutes. Remove to a plate; keep warm.
Add onion and garlic to skillet and cook 1 minute. Add broccoli, red pepper, mushrooms and celery; cover and cook, stirring occasionally, for 8 minutes or until broccoli is tender.
Stir in beef, any accumulated juices and soy sauce mixture. Heat through, about 2 minutes. Sprinkle peanuts over the top.
Serve immediately with cooked white rice.