Place chickpeas, soaking liquid, and 3/4 teaspoon salt in a large pot. Liquid should cover by 2 inches; adjust as necessary. Bring to a boil. Reduce heat, and simmer gently. Cook, stirring occasionally, until chickpeas are tender, about 40 minutes. Drain, and transfer to a bowl. (Makes 3 cups chickpeas.)
Meanwhile, using a chef's knife, press flat side of blade back and forth across garlic and remaining 1/2 teaspoon salt to make a paste. Transfer to a bowl, and whisk in peppercorns, vinegar, oil, and oregano. Pour dressing over chickpeas. Let stand, stirring once or twice, for 30 minutes. Toss in tomatoes, cucumber, bell pepper, carrots, scallions, parsley, and basil.