In a mixing bowl, combine olive oil, minced garlic, soy sauce, Worcestershire sauce, smoked paprika, ground black pepper, salt, and dried oregano. Mix well to create a marinade.

Add the cubed sirloin steak to the marinade, ensuring all pieces are well-coated. Cover and refrigerate for at least 30 minutes, or up to 2 hours for more flavor.

In a small bowl, combine melted butter, minced garlic, chopped parsley, and lemon juice. Stir well and set aside.

If using wooden skewers, soak them in water for at least 30 minutes to prevent burning on the grill.

Preheat the grill to medium-high heat.

Thread the marinated steak cubes onto the skewers, alternating with pieces of bell peppers, red onion, and mushrooms.

Place the skewers on the preheated grill. Cook for about 10-15 minutes, turning occasionally, until the steak is cooked to your desired level of doneness (135°F for medium-rare, 145°F for medium).

During the last few minutes of grilling, brush the kabobs generously with the garlic butter to enhance flavor.

Remove the kabobs from the grill and let them rest for a few minutes before serving.

Drizzle any remaining garlic butter over the kabobs and garnish with additional chopped parsley if desired.