Preheat oven to 350 degrees Fahrenheit.

Melt butter in an oven-proof Dutch oven or large frypan with oven-proof lid.

Sauté onions, garlic, celery, and green pepper until softened (4-5 minutes).

Add rice and mix with wooden spoon for 3 minutes.

Carefully add chicken broth, diced tomatoes (with juice), seasoning salt, pepper, cayenne pepper, sliced olives, frozen peas, and sliced mushrooms.

Stir to combine and simmer on low heat for 5-6 minutes until mixture boils.

Cover with tight-fitting lid.

Place in oven to cook for 30-35 minutes or until rice is tender.

Fluff with a fork.

Serve and enjoy!