You will need a LARGE tray for this!
Cut mozzarella cheese and tomatoes into 1/4" slices. Layer tomatoes on the tray with slice of mozzarella on top and top each one with a basil leaf. Crumble bleu cheese and layer over tomatoes and cheese. Slice avocado into small crescent moon shapes and layer it on the mixture. In a a small bowl, mix olive oil and balsamic and drizzle over tomato mixture. Sprinkle ground pepper. Serve immediately.
Note: If you want to chill for guest arrival, do not slice or put avocado on until last and drizzle the balsalmic mixture on right before serving. The best way to store a large tray to chill is to dampen paper towels and lay over the mixture. This will keep it cooler and keep it from drying out. I love this with a big loaf of bread but that is not necessary! Enjoy!