COOK spaghetti as directed on package, adding snap peas and red pepper to the cooking water for the last 2 min. of the spaghetti cooking time.
MEANWHILE, heat dressing in large skillet on medium-high heat. Add meat; stir-fry 3 min. or until meat is barely pink in center. Add peanut butter and soy sauce; stir-fry 1 min. or until sauce thickens.
DRAIN spaghetti and vegetables. Add to skillet; toss with meat mixture. Stir in green onions; sprinkle with peanuts.