Preheat oven to 375. Preheat large iron skillet to medium.
Add bread crumbs and shredded cheese into a 1/2 measuring cup, cover and shake to mix. Set aside.
Melt 1-stick margarine in microwave. Set aside.
Using the 1/2-stick margarine, coat a 9x13 casserole dish on the bottom and a little up the sides. Put the remainder of the 1/2 stick margarine into the skillet.
Chop and add to the skillet: squash, onion and all peppers. Add frozen vegetables. Stir, cover, stir often while completing next step.
In a large bowl (one size bigger than the one you picked), combine crushed crackers, grated cheese, eggs, evaporated milk, melted margarine, salt and pepper. Add warm/softened vegetables from skillet and stir thoroughly.
Pour into casserole dish and bake at 375 for 45 minutes. After 35 minutes, remove the casserole and top with cheese/bread crumb mixture. Return to oven.
For a more moist casserole, add 1 can of Rotello tomatoes. (I warned you about the big bowl!)
Substitute 2 handfuls of your favorite Dorito chips (crushed) for 1 sleeve of crackers.
If you can't find frozen Southwest veggies, use corn, black beans, poblano peppers and onions, to total 12 oz.
Add one to four dashes of Texas Pete hot sauce before the final stir, if that's your pleasure.
Feel free to add your favorite spices to the veggie skillet. I use rosemary and crushed garlic.