HEAT OVEN TO 350°F. GREASE OR SPRAY 13×9-INCH PAN.
IN LARGE BOWL, PLACE 1 LB COOKED AND DRAINED PENNE PASTA, 2 CUPS SHREDDED COOKED CHICKEN, 1 JAR (15 OZ) ALFREDO PASTA SAUCE AND 1/2 CUP RANCH DRESSING. STIR TO COMBINE. POUR MIXTURE IN PAN; SPREAD EVENLY.
SPRINKLED 6 SLICES CHOPPED COOKED BACON EVENLY OVER TOP, THEN SPRINKLE WITH 2 CUPS SHREDDED MOZZARELLA CHEESE (8 OZ).
BAKE 15 TO 20 MINUTES OR UNTIL HOT AND BUBBLY. LET STAND 5 MINUTES BEFORE SERVING. SPRINKLE WITH CHOPPED PARSLEY.