In a large bowl, whisk together olive oil, soy sauce, Worcestershire sauce, lemon juice, garlic powder, onion powder, paprika, salt, and pepper.
Add the steak cubes and shrimp to the marinade, tossing to coat. Cover and refrigerate for at least 30 minutes, or up to 2 hours for more flavor.
Preheat the grill to medium-high heat. If using wooden skewers, soak them in water for 30 minutes to prevent burning.
Thread the marinated steak, shrimp, red bell pepper, green bell pepper, and onion onto the skewers, alternating between the ingredients.
Place the kabobs on the grill and cook for 10-12 minutes, turning occasionally, until the steak is cooked to your desired doneness and the shrimp are pink and opaque.
Remove the kabobs from the grill and let them rest for a few minutes before serving.