Roughly chop the garlic and then add the oregano, salt and pepper. Chop the mixture together and use the side of a knife or a mortar and pestle to make a grainy herb paste.
Transfer the paste to a large salad bowl, and add the lemon juice and vinegar. Mix with a fork, allowing the salt to dissolve, then add the oil and whisk with a fork until well combined. The dressing should be thick with garlic and oregano.
Gently fold the chickpeas, red onion, provolone, salami, pepperoncini (including seeds and juice) into the dressing, one at a time.
Halve the tomatoes lengthwise and season with 1 1/2 teaspoons salt. Set aside until ready to serve.
When ready to serve, gently add the tomatoes, lettuce and radicchio to the salad bowl, along with a couple of generous pinches of oregano, and toss to combine with the dressing. Serve immediately.