Combine ingredients: In a large bowl, combine beef cubes, red onion, green bell pepper, olive oil, lemon juice, garlic, oregano, salt, and pepper. Toss to coat.

Assemble kebabs: Thread the marinated beef, onion, and bell pepper onto metal skewers.

Grill kebabs: Preheat your grill to medium-high heat. Grill kebabs for 10-12 minutes, or until the beef is cooked through and slightly charred.

Serve: Serve immediately with your favorite dipping sauce, such as tzatziki or hummus.

Tips:

For a spicier kebab, add a pinch of red pepper flakes or cayenne pepper to the marinade.

You can substitute other vegetables for the red onion and green bell pepper, such as mushrooms, zucchini, or cherry tomatoes.

Serve kebabs with a side of grilled vegetables or a salad.

Enjoy your delicious beef kebabs!