Preheat your oven to 400°F (200°C).

Prepare a large baking sheet with aluminum foil or parchment paper and lightly spray it with nonstick cooking spray.

In a large mixing bowl, combine the frozen hash browns, shredded cheese, diced onion, olive oil, melted butter, salt, and pepper. Stir until evenly coated.

Spread the mixture evenly onto the prepared baking sheet.

Bake for about 28 minutes, checking occasionally for a golden-brown color.

Once golden and crispy, remove from the oven, let cool for a minute, then cut into squares and serve hot.