Prep oven and dish: Preheat oven to 375°F. Grease a 9x13 baking dish.
Brown the sausage: In a large skillet over medium-high heat, brown 1 pounds Italian sausage, casings removed (hot or sweet), breaking it into crumbles, about 8 minutes 08:00. Add 3 garlic cloves, minced in the last minute and stir until fragrant.
Wilt the spinach: Add 5 ounces baby spinach to the skillet and stir until just wilted, about 2 minutes 02:00. Remove from heat.
Whisk the egg base: In a large bowl, whisk together 12 large eggs, 1 cups heavy cream, 1 teaspoons salt, 0.5 teaspoons black pepper, and 1 teaspoons dried oregano.
Assemble: Spread the sausage and spinach mixture evenly in the baking dish. Scatter 0.5 cups oil-packed sun-dried tomatoes, drained and chopped and 4 ounces cream cheese, softened and cubed over the top. Pour the egg mixture over everything.
Top and bake: Sprinkle 1 cups shredded provolone, 0.5 cups grated parmesan, and 0.5 teaspoons crushed red pepper flakes over the top. Bake until the center is set and the top is golden, 35 minutes 35:00.
Cool and store: Let cool 10 minutes before slicing. Keeps refrigerated for up to 5 days; reheat individual squares in the microwave or a 350°F oven.