Heat a medium saucepan over medium heat; swirl in oil. Add garlic and red-pepper flakes and cook, stirring, 1 minute. Add escarole, toss to coat, and season with salt. Cook until escarole is just wilted, about 2 minutes.
Add kidney beans, chickpeas, broth, and 2 cups water and bring to a simmer. Cook until heated through, about 3 minutes. Season with salt; remove garlic. Top with toasted bread and red-pepper flakes. Serve immediately, with lemon wedges.