Combine the beans, roasted peppers, pickles, celery, parsley, and lemon zest juice in a large bowl.
Heat the olive oil in a large skillet over medium-high heat. Add the chicken and thyme, then scatter the red onion and red papper flakes around the pan, Cook until the chicken is browned on the bottom and the onion is soft, about 4 minutes. Turn the chicken, add 1/4 cup of water, cover the skillet and reduce the heat to low. Continue cooking until the chicken is cooked through, 5-8 more minutes. Transfer the chicken to a cutting board; discard the thyme. Add the cooked onion to the bean mixture.
Thinly slice the chicken against the grain and add to the bean mixture. Add the greens and toss to combine.