Make the marinade in a bowl, a marinade tray, or a zip bag by combining all the ingredients. Alternatively, use your favorite store-bought marinade to infuse your kabobs with flavor.
Place the cubed beef in the zip bag, tray, or bowl. Transfer it into the fridge for 30 minutes or overnight. If you have a marinade tray, you can assemble the skewers and marinade them assembled.
Remove the beef cubes from the marinade and discard the marinade.
Assemble:
Alternate threading the beef, onions, bell peppers, and mushrooms onto each skewer, about 3 pieces of each per kabob.
Cook:
Heat a large cast-iron skillet or pan over medium-high heat. Once hot, grease the pan or spray the kabobs. Place the kabobs on the hot surface, about 4 per batch, and cook for 2 to 3 minutes per side, flipping them around until cooked through.
After cooking the kabobs on two sides, you can cover the pan, reduce the heat to medium, and finish cooking the kabobs. Covering the pan traps the heat and helps ensure the veggies cook through.
Serve:
Remove the kabobs from the pan and serve with your favorite sides.