Preheat oven to 350 degrees F. Using a small damp wash cloth clean all the mushroom caps.
Remove the mushroom caps from 16 ounces of baby Bella mushrooms and set aside. Dice the remaining eight ounces with the mushroom caps; set aside.
In a large sauté pan over medium high heat add one tablespoon of olive oil. Add in chopped onions, peppers, and chopped mushrooms. Sauté until the mushrooms have browned, stirring frequently, about seven minutes. Add salt and pepper to taste and remove from sauté pan.
In the same sauté pan add an additional tablespoon of olive oil. Add chorizo, breaking into chunks as the chorizo cooks. Continue to cook chorizo until browned, about 10 minutes; stirring occasionally. Add the mushroom mixture back into the pan and stir to combine.
Put mushroom caps on a prepared baking pan. Add one to two tablespoons of chorizo mixture to each mushroom cap. Top each mushroom with Mexican blend cheese. Bake at 350 degrees for 10 minutes until the cheese has melted and the mushroom have warmed through.