Place chicken legs in a large plastic bag or bowl. Pour Italian dressing over the top, tossing to combine. Cover with plastic wrap (if using bowl) and marinate for at least two hours--several hours is better. Toss a few times during the marinating process.
Preheat broiler to high. Arrange oven rack toward bottom of oven.
Lay chicken legs on a broiler pan, or other baking dish with a drip tray. Sprinkle Ranch seasoning on both sides and broil for 25 minutes, turning once and marinating other side with Ranch seasoning halfway through. Remove pan from oven when done.
Serve immediately with Ranch dipping sauce and enjoy!