Step 1

Slice sweet onions into ¼ in thick slices. Seperate the onion rings and spread in a greased 9x13in baking dish.

Step 2

Sprinkle onion rings with salt, garlic powder, and oregano.

Step 3

Thinly slice butter and arrange evenly over the onions.

Step 4

Evenly layer cheddar, mozzarella, and parmesan cheese over the onions.

Step 5

Bake onions uncovered at 350 degrees for 35-40 minutes. Serve.