Cut the meat, onion and pepper into large bite-sized pieces, and cut the mushrooms in half. Thread the pieces of meat onto wooden skewers, alternating with pieces of onion, pepper and mushroom.
Drizzle the kabobs with olive oil, season liberally with salt and pepper.
Grill on pre-heated cast iron grill. Rotate skewers every so often so that they grill evenly for 8-10 minutes.
Set the broiler to "Hi". Place the kabobs on a broiler pan and put it on a rack adjusted so the kabobs are about 4-6 inches below the broiler. Cook for about two minutes until the meat is browned, then turn everything over and cook the other side until browned.
3 pounds of meat (sirloin, chicken or shrimp), cubed
1/2 large sweet onion, cut in large chunks
2-3 large peppers, cut in chunks
1/2 pound white button mushrooms (optional), whole
1 pint cherry tomatoes (optional), halved or whole