For the best, juicy, and tender lemon baked chicken breasts remember these three things: marinate first, bake loosely covered, and use a meat thermometer. Before baking in the oven, we marinate the chicken breasts in a magical mixture of fresh lemon, garlic, Dijon mustard, and parsley. If you’re short on time, marinate as close to an hour as you can. If you’re flexible, go for a whole two hours. And since we want to keep things safe, it’s best to marinate the chicken in the refrigerator (no matter how long you do it for).