In a large saucepan of barely boiling salted water, cook the sausages for 3 minutes. Remove the pan from the heat and let the sausages cool in the liquid. Refrigerate.
Marinate the chicken. Spoon enough salsa verde over the chicken to coat evenly.
Marinate the lamb in the same fashion as the chicken. Let both meats marinate chilled in separate containers for about 8 hours.
Before grilling let the sausages, chicken, and lamb sit at room temperature for 20 to 30 minutes.
Preheat the grill to high. Clean the grate with a brass-bristle brush. Reduce the heat to medium.
Lightly coat the sausages with oil. Season the chicken on all sides with 2 teaspoons salt, pressing it into the meat. Season the racks of lamb on all sides with 2 teaspoons salt, pressing it into the meat. Season the cut side of the lemons with 1/2 teaspoon salt and 1/4 teaspoon pepper.
Grill the chicken and lamb racks over direct medium heat until well browned on all sides, 6 to 8 minutes, turning occasionally. Move the chicken and lamb to indirect heat and continue to cook for 10 more minutes. Leaving the chicken and lamb rack to continue cooking over indirect heat, grill the sausages over direct medium heat for about 6 to 8 minutes. Move the sausages to indirect heat to finish cooking for 4 to 6 minutes. Season the summer squash with olive oil, salt and pepper, and grill over direct heat until caramelized and fully cooked. During the last few minutes of grilling, grill the lemons cut side down over direct medium heat until well browned, about 2 minutes.
Remove everything from the grill and let the rest at room temperature for 5 to 10 minutes. Cut the meats into serving-size pieces. Arrange on a large platter and garnish with the lemons and salsa verde. Guests
For the salsa verde:
Soak the slices of bread in 2 tablespoons vinegar for 1 minute. Using a food processor blend all ingredients together, taste for seasoning and adjust consistency if need be.