Meanwhile, cook chicken and onions in hot oil in large skillet on medium heat 6 to 8 min. or until chicken is done, stirring frequently. Add peas, peppers and garlic; cook and stir 1 min. Add milk and cream cheese; cook and stir 3 to 4 min. or until cream cheese is completely melted and sauce is well blended, stirring constantly. Stir in Parmesan.