Add all marinade ingredients into the blender and blend until smooth.
Place beef, red onion and bell pepper pieces into a large zip-lock bag, pour the marinade mixture in, close it and mix until everything is combined. Refrigerate for 2 hours or over night.
Thread beef with red bell pepper and onion onto metal skewers. Grill on a preheated grill for 3-4 minutes on each side, or until desired doneness. Enjoy!
Video
Notes
When cutting the beef, make sure to cut against the grain into strips and then into cubes. This will shorten the muscle fibers and ensure a more tender bite.
You can leave everything to marinate overnight if you want, or you can prepare it in the morning and have it ready to grill for dinner at the end of the day.
When skewering the meat and veggies, do it loosely, leaving a bit of space between each piece so that the beef cooks evenly on all sides of the cube.
Feel free to use a different skewer pattern. For example, 1 cube of beef, 2 peppers, 1 onion is another way to add them onto the skewer!