Spread the thawed shredded hashbrowns evenly across the bottom of a 9×13 inch baking dish.
In a large skillet, cook the savory ground breakfast sausage over medium heat until browned and cooked through. Drain any excess fat. Add diced bell peppers and sliced mushrooms to the skillet; sauté until tender-crisp. Stir in chopped asparagus and steamed broccoli. Transfer the mixture to a large bowl and fold in shredded sharp cheddar and pepper jack cheese. Spread this mixture evenly over the hashbrown layer in the baking dish.
In a separate large bowl, whisk together the eggs, milk, onion powder, garlic powder, salt, and black pepper until well combined and slightly frothy.
Carefully pour the whisked egg mixture over the hashbrown, sausage, and vegetable layers in the baking dish, ensuring the liquid permeates all layers. Gently press down on the ingredients if needed. Bake in a preheated oven at 375°F (190°C) for 50-60 minutes, or until golden brown and the eggs are fully set. Let rest 5-10 minutes before serving.