Heat oven to 400° F. In a large bowl, toss the chicken and mustard to coat.
In a separate bowl, mix the cereal, 1 tablespoon of the oil, and 1/4 teaspoon each salt and pepper. Coat the chicken with the cereal mixture and bake on a baking sheet until golden and cooked through, 45 to 50 minutes.
Meanwhile, cook the collards in a large pot of boiling salted water until tender, about 10 minutes. Drain, rinse, and squeeze out the excess water.
Heat the remaining oil in a skillet over medium heat. Add the garlic, collards, and 1/4 teaspoon each salt and pepper. Cook for 2 to 3 minutes. Serve with the chicken and lemon.