Finely dice the ¼ cup finely diced red onion, ½ cup finely diced green pepper, and 1 jalapeno.
Stir the 32 oz. sour cream, 2 packages fiesta Ranch dip mix, 8 oz. shredded Mexican cheese, 1 10 oz. can drained Rotel, and 1 4 oz. can drained diced green chiles together in a large mixing bowl. Fold in the chopped veggies.
Cover and refrigerate for at least an hour to let the flavors meld.