In a large glass bowl, whisk together the olive oil, lemon juice, oregano, rosemary, garlic, lemon zest, bay leaf, salt and a few grinds of pepper. Put the beef cubes in the marinade and toss to coat. Cover. Refrigerate and marinate for 2 hours, turning the beef a couple of times to make sure it’s evenly marinating.
Remove the beef from the steak marinade- discard the bay leaf, but keep the marinade.
PREPARE THE KABOBS:
Assemble the kebabs by alternating cubes of beef with bell pepper and onion and mushroom. Lay the prepared kebabs in a shallow dish and brush with the reserved marinade.
Preheat the grill to medium. Grill 8 to 10 minutes until the beef is just medium-rare, turning the skewers several times for even cooking.