In a gallon-size food storage bag, combine the olive oil, rosemary, balsamic vinegar, lemon juice, dijon mustard, garlic, salt, and pepper. Squeeze the bag and smush the marinade ingredients together until combined.
Cut sirloin steaks into 1-inch cubes. Add the steak cubes to the marinate, press out any air in the bag, and seal tightly. Refrigerate for at least 6 hours.
Preheat your grill to medium-high heat.
Assemble the kabobs by arranging the steak and vegetables onto metal skewers in an alternating pattern. Try to keep the amount of meat and veggies even on the kabobs so each one has the same amount of each.
Lay the skewers directly on the hot grill. Rotate every few minutes until all sides are cooked evenly and the veggies are lightly browned, about 10-12 minutes of total cooking time.
Remove the kabobs from the grill to a platter. Serve on the skewer or remove the meat and veggies from the skewers before serving warm with your favorite sides.
Notes
Nutritional information may vary by kabob.
If you end up with extra vegetables, you can make all veggie kabobs. Brush them with a little olive oil and season with salt and pepper before grilling with the steak kabobs.