A delightful baked dish combining zucchini and yellow squash with a cheesy topping.
Preheat your oven to 375°F (190°C).
Ensure the oven is fully preheated for even cooking.
Slice the zucchini, yellow squash, and onion into thin rounds.
Use a mandoline slicer for uniform slices.
In a mixing bowl, combine the sliced vegetables with salt, pepper, and oregano.
Toss gently to ensure even coating of the seasonings.
Grease a baking dish with butter and layer the seasoned vegetables evenly.
Press the vegetables down slightly to create a compact layer.
Sprinkle the grated Parmesan and shredded cheddar cheese evenly over the top.
Mix the cheeses beforehand for an even distribution.
Bake in the preheated oven for 30 minutes, or until the cheese is golden and bubbly.
Check halfway through to ensure the cheese doesn't overbrown.
Let the casserole cool for 5 minutes before serving.
Cooling allows the flavors to meld and makes serving easier.