Get Ready: Preheat your oven to 350°F (175°C). Lightly spray a 9x13 inch casserole baking dish with olive oil for easy cleanup.
Brown the Sausage: In a large skillet, cook the Italian sausage over medium heat until it's nicely browned and crumbled. Once done, remove it from the skillet and set it aside to cool slightly.
Sauté the Veggies: In the same skillet (don't worry about cleaning it, those drippings add flavor!), melt the butter. Add the diced red bell pepper, onion, a pinch of salt, and half of the black pepper. Cook until the vegetables are tender and softened, then set them aside to cool.
Whisk the Eggs: In a large mixing bowl, whisk together the eggs, heavy cream, garlic salt, and the remaining black pepper until everything is well combined and a little frothy.
Layer It Up: Pour half of the whisked egg mixture into your prepared baking dish. Evenly scatter half of the cooked sausage, sautéed peppers and onions, shredded Italian cheese, and small dollops of cream cheese over the eggs.
Second Layer: Repeat the layering with the rest of the ingredients, making sure to finish with a generous sprinkle of shredded cheese over the top for a golden crust.
Bake to Perfection: Place the casserole in your preheated oven and bake for about 30 minutes, or until the eggs are completely set and firm in the center.
Cool & Serve: Let the casserole cool for about 10 minutes before slicing and serving. This helps it set perfectly for clean cuts!