BRING 1-1/4 cups water and 2 Tbsp. dressing to boil in large skillet on medium-high heat. Stir in stuffing mix, spinach and peppers; cover. Remove from heat. Let stand 5 min.; stir. Transfer to serving platter; cover to keep warm.
HEAT oil in same skillet on medium heat. Add meat; cook 12 to 15 min. or until done (145ºF) and evenly browned, turning frequently. Let stand 3 min. Place over stuffing; cover.
MIX remaining dressing, mustard and water. Add to skillet with Neufchatel; stir. Cook until Neufchatel is completely melted and mixture is well blended, stirring constantly with whisk. Serve over meat.