My Mom's Swiss Steak - Chefwiz

Ingredients

• 2 tbsp vegetable oil
• 2 (1/2 lb) beef sirloin tip steaks
• Salt and pepper to taste
• 1 cup chopped onion
• 1 (16 oz) can diced tomatoes
• 2 cups sliced fresh mushrooms (optional)
• 1 stalk celery (, chopped (optional))
• 1/2 cup chopped green bell pepper (optional)
• 1 1/2 tsp dried oregano
• 1 bay leaf
• 1 cup water (optional)
• 2 tbsp cornstarch (optional)