Heat olive oil in a large skillet over medium-high heat. Add the crumbled soy sausage and cook until lightly browned, about 3-4 minutes. Add the onion, garlic, oregano, and red pepper flakes and cook until the onion is softened, about 3 minutes. Add the spinach and cook until wilted, about 1 minute.
In a large bowl, whisk together the eggs, milk, salt, and pepper. Add the bread cubes and stir to combine. Add the cooked sausage mixture and stir until everything is evenly combined.
Pour the mixture into a greased 9-inch square baking dish. Sprinkle the Parmesan and mozzarella cheese on top. Bake for 25-30 minutes, or until the top is golden brown and the center is set.
Let cool slightly before serving.
Interesting Facts
Strata is a classic Italian dish that is traditionally served for brunch.
This dish is a great way to use up leftover bread and vegetables.
You can substitute the soy sausage with any type of sausage or even cooked bacon.