Melt margarine in 12-inch nonstick skillet over medium-high heat and cook chicken, stirring occasionally, 4 minutes until chicken is thoroughly cooked. Remove chicken from skillet and set aside.
Stir water and Knorr® Rice Sides - Buffalo Chicken into same skillet and bring to a boil over high heat. Reduce heat to low and simmer covered 7 minutes.
Stir in chicken and simmer an additional 2 minutes or until rice is tender and chicken is heated through. Stir in celery and Dressing. Remove from heat and let stand covered 2 minutes. Garnish, if desired, with thinly sliced green onions.