Preheat oven to 350 degrees F (175 degrees C). (Note - you don't absolutely have to bake this mac and cheese if you are pressed for time - simply skip steps 7 and 8)
In a large skillet, heat the olive oil over medium heat, add the beans and veggies and cook until warmed through and slightly softened.
1 tablespoon olive oil, ½ cup black beans, drained and rinsed, ¾ cup corn, 2 cups frozen pepper and onion strips
Add the cumin, chili powder, and cayenne and mix while heating. Set aside.
1 ½ tablespoons cumin, 1 ½ tablespoons chili powder, ⅛ teaspoon ground cayenne pepper
Melt the butter in a saucepan over medium heat, mix in the milk, then the flour.
2 tablespoons butter, 2 cups milk, ¼ cup flour
Add the cheese and stir until melted.
3 cups shredded fiesta blend cheese
Add the cooked pasta into the skillet with the veggies, then pour the cheese sauce on top and mix well. (NOTE-If you are NOT baking this, at this point you can sprinkle the bread crumbs on top and serve.)
7 cups elbow macaroni, cooked
Pour the mac and cheese into a 9x9 baking dish.
Sprinkle with the bread crumbs. Cover with foil and bake for 20 minutes, then remove foil and bake for another 10 minutes. Keep an eye on it to prevent burning.
¼ cup seasoned bread crumbs
Notes
For a shortcut, use a 12 ounce package of frozen southwest blend vegetables instead of the beans, corn, and pepper and onion strips.
You can change up the cheese as you prefer: Cheddar is a classic choice, but you can also add Monterey Jack for creaminess and some sharpness with a bit of pepper jack for more of a kick.
Other ideas for variations are to add diced green chilies, roasted poblano peppers, or jalapeños.
Chopped cilantro, green onions, or fresh tomatoes can also be sprinkled on top after baking for added freshness.
Use freshly grated cheese for easier melting and a smoother consistency.