Preheat your oven to 375°F.
Set the oven rack in the middle for even browning.
In a large bowl, blend the softened cream cheese, sour cream, and mayonnaise with a hand mixer until mostly smooth.
A few lumps? No big deal!
Add the Parmesan, Romano, white cheddar, and provolone cheeses right into that creamy mix.
Stir until it all comes together.
Now fold in the spinach, garlic, salt, pepper, and a pinch of crushed red pepper if you want a little heat.
Mix until the spinach looks spread throughout.
Spoon the mixture into an oven-safe baking dish and smooth it out.
Scatter a bit more Parmesan and cheddar on top for a golden, cheesy crust.
Bake for 20–25 minutes, until it bubbles and the top turns golden and crisp at the edges.
Let it sit for about 5 minutes before serving so it sets up a bit.