Preheat an oven to 350 degrees F (175 degrees C). Lightly grease a 9×13 inch baking dish and set aside.
Fill a saucepan with water, bring to a boil over medium heat, and boil the Brussels sprouts and broccoli for 2 minutes, until thawed. Add the asparagus, and boil for 3 more minutes, until the vegetables are hot, lightly cooked, and bright green.
Drain the Brussels sprouts, broccoli, and asparagus, place into the prepared baking dish, and dot with butter. Stir to melt the butter, and mix in the spinach, garlic powder, black pepper, and bread crumbs.
Bake in preheated oven for 10 minutes to heat the vegetables, remove from the oven, and stir in the Cheddar cheese. Return to the oven, and bake for 20 minutes or until cheese is melted, spinach is cooked, and casserole is hot.