COOK spaghetti as directed on package, omitting salt and adding snap peas and pepper strips to the boiling water for the last 2 min.
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 onions; sprinkle with nuts.