Season both sides of the tenderized beef round steak pieces with salt and pepper.

Place the all-purpose flour in a shallow dish. Dredge the seasoned steak pieces in the flour, shaking off any excess.

In a large skillet or Dutch oven, heat vegetable oil over medium-high heat. Add the dredged steak pieces to the skillet and cook until browned on both sides, about 3-4 minutes per side. Remove the browned steak pieces from the skillet and set aside.

In the same skillet, add sliced onion, sliced green bell pepper, and sliced mushrooms. Cook, stirring occasionally, until the vegetables are softened, about 5-6 minutes.

Add minced garlic to the skillet and cook for an additional 1 minute, until fragrant.

Stir in diced tomatoes (including the juice), beef broth, Worcestershire sauce, dried thyme, and paprika. Bring the mixture to a simmer.

Return the browned steak pieces to the skillet, nestling them into the sauce and vegetables.

Cover the skillet with a lid and reduce the heat to low. Simmer the Swiss Steak for 1 1/2 to 2 hours, or until the steak is tender and the sauce is thickened, stirring occasionally.

Once the Swiss Steak is cooked through, taste the sauce and adjust seasoning if necessary.

Garnish the Swiss Steak with fresh parsley, if desired, before serving.