In a large pot over medium heat, melt butter.

Add chopped onions, celery, and red bell pepper to the pot.

Cook the vegetables in butter until tender, about 3-5 minutes.

Remove the cooked vegetables from the pot and set aside.

In the same pot, cook the shrimp until they turn pink and are just a touch undercooked.

In a large bowl, combine the cooked vegetables, cream of mushroom soup, cooked rice, salt, and pepper.

Add swiss cheese and half of the cheddar cheese to the bowl.

Mix all ingredients in the bowl well.

Lightly grease a 9x13 inch baking tray.

Pour the rice mixture into the prepared baking tray.

Arrange the cooked shrimp throughout the baking tray, nestling them into the rice mixture and ensuring they are covered.

Cover the baking tray with foil.

Bake in a preheated 375F oven for 30 minutes.

Remove the foil cover.

Sprinkle the remaining cheddar cheese over the casserole.

Bake uncovered for 5 minutes, or until the cheese is melted and bubbly.

Serve hot with wedges of fresh lemon.