Beef souvlaki with tzatziki sauce (kebabs)

2 lb Beef or lamb cut into 1"
           -cubes (I use lamb)
     12    Cherry tomatoes or tomato
           -wedges
      1 ts Black pepper
      1 ts Oregano
      2    Cloves garlic, finely
           -minced
      6 tb olive oil
      2 md Onions, quatered
      2 md Green peppers, cut into 1"
           -pieces
     12    Fresh mushrooms
      4 tb Lemon juice
           Salt to taste
           Skewers
 
  This recipe takes two days. On the first day, prepare the meat and
  marinate. On the second day, prepare the veggies and cook.
  Place meat in a bowl. In a small bowl, combine black pepper, garlic
  and oregano and sprinkle mixture over meat. Mix well to coat.
  In a blender, combine lemon juice and olive oil and blend. Pour over
  meat, cover and refrigerate overnight.
  The next day, brush onions and green pepper with olive oil and
  sprinkle with salt and pepper to taste. Thread meat and veggies,
  alternating, on to skewers. Barbecue on grill, being careful not to
  overcook. Use remaining marinate to bush on while cooking. Before
  serving, sprinkle with salt and fresh lemon juice.