In a small bowl, combine 2 cloves of garlic, the rosemary and 1 tablespoon of the oil. Spoon mixture evenly over pork; rub in with your fingers.
In the same bowl, combine remaining clove of garlic, remaining 1 tablespoon of oil, oregano, lemon peel and lemon juice. Brush over zucchini, yellow summer squash, onion and bell peppers.
Preheat oven to 425 degrees.
Place rack in center of a large shallow roasting pan. Place tenderloin on rack. Arrange seasoned vegetables around edge of pan. (Vegetables don't need to be on rack.) Roast for 30 to 40 minutes, or until an instant-read thermometer inserted into center of tenderloin registers 155 degrees. Remove tenderloin from roasting pan. Cover with foil and let stand 10 minutes before slicing. The temperature of the meat after standing should be 160 degrees.
Transfer vegetables to a very large serving bowl; add tomatoes, capers and basil. Toss to combine. Season to taste with kosher salt and black pepper. Cover and let stand until pork is ready to serve.
Cut pork into 1/4-inch slices. Serve pork on top of vegetables, over 1/2 cup whole-grain rotini or other small pasta.