In a large bowl, combine the beef cubes, red and yellow bell peppers, onion, olive oil, garlic powder, onion powder, smoked paprika, salt, and pepper. Toss to coat the beef and vegetables evenly. Cover and marinate in the refrigerator for at least 30 minutes, or up to 2 hours for more flavor.
While the beef is marinating, prepare the chimichurri. In a medium bowl, mix together the parsley, olive oil, red wine vinegar, minced garlic, red pepper flakes, salt, and pepper. Adjust seasoning to taste. Set aside.
Preheat your grill to medium-high heat. Thread the marinated beef and vegetables onto skewers, alternating between beef and veggies.
Grill the skewers for about 10-12 minutes, turning occasionally, until the beef is cooked to your desired doneness and the vegetables are tender.
Remove the skewers from the grill and let them rest for a few minutes. Serve warm, drizzled with chimichurri sauce.