To prepare the marinade, in a large bowl, combine olive oil, soy sauce, balsamic vinegar, Worcestershire sauce, Dijon mustard, honey, garlic, kosher salt, and ground black pepper. Whisk thoroughly to combine.
Pat dry sirloin steak (or roast) and pierce, using a fork, gently into a few places. Cut it into 1-inch cubes.
Place the cubed beef into the bowl with the marinade. Toss to ensure that all beef cubes have direct contact with the marinade. Seal tightly using stretch film. Refrigerate for a minimum of 6 hours or overnight.
If using wooden skewers, soak them in water for 30 minutes before assembling the steak kabobs. If using metal skewers, you can skip this step.
Arrange the oven rack in the middle position and preheat the oven to 375 degrees F /190 degrees C. Line a rimmed baking sheet with parchment paper and set it aside.
Loosely thread the beef chunks on the skewer tapping off any excess marinade, and alternate with the onion and peppers. For 1 ½ pounds of cubed beef, you should have 11-12 skewers, with each skewer having 3-4 pieces of meat (depending on the size of the beef cubes.)
Transfer the beef kabobs onto the prepared baking sheet. Discard the marinade.
Bake the beef kabobs in the preheated oven for 10 minutes, flipping halfway. When done, turn the broiler on and broil the kabobs for 3-4 minutes, making sure to turn them once halfway through the process for even browning.
Remove from the oven and loosely tent with foil. Let the meat rest for 5 minutes before serving.