Step 1

In a medium bowl, mix the marinade ingredients together.  Reserve 1 tablespoon of the marinade.

Step 2

Place the cubed meat into a large plastic zip-tight bag and pour all but the reserved marinade over it, then seal and squish to coat well.  Place in the refrigerator for 1-6 hours to marinate.  This is also a good time to place wooden skewers in water to soak.

Step 3

Meanwhile, boil the potatoes in a large pot of salted water until just tender enough to pierce with a fork, about 6-8 minutes. Drain well, then toss with 2 tablespoons of olive oil, rosemary, and mustard.  Set aside.

Step 4

Preheat grill to high heat while preparing the kabobs.  Chop all vegetables into chunks that are roughly the same size as the cubed steak, keeping 3 layers of onion together in each chunk.  Drizzle vegetables with the reserved marinade.

Step 5

Thread alternating pieces of meat, vegetables, and potatoes until the skewers are filled, aiming for 4-5 pieces of steak on each skewer.

Step 6

Place kabobs on the grill directly over the heat and reduce heat to medium-high.  Grill for 8-10 minutes, flipping every 2-3 minutes, until the meat is cooked medium-rare to medium and the vegetables start to char just around the edges.

Step 7

Remove from the grill and rest for 5 minutes before serving.