Preheat the oven to 400°F. Line a rimmed baking sheet with parchment paper or aluminum foil.

Set the cabbage upright on a cutting board then, using a sharp knife, slice the cabbage from the top down into 1-inch thick rounds. Arrange the cabbage in a single layer on the prepared baking sheet.

In a small bowl, whisk together the olive oil, garlic powder, oregano, salt, and black pepper. Use a silicone brush to brush the oil mixture over the cabbage.

Roast for 30 minutes, or until the outer leaves are charred and the centers of the cabbage steaks are fork-tender. The cooking time may vary slightly depending on your preference for a crispy or more tender cabbage steak. Adjust seasoning to taste, sprinkle with fresh parsley, and serve hot.