I’m more of a sheet pan cook, but my family is not on my side.
They prefer dinners baked in a casserole dish, so at least once a week, usually for Sunday dinner, I make one for them.
This baked mustard chicken casserole has tender chicken thighs, roasted red peppers, and a sweet mustard marinade, with toasted almonds scattered over the top.
Why This Chicken Casserole Works
Chicken thighs stay tender. They are more forgiving than chicken breasts and remain juicy after baking. Boneless thighs also cook quickly and are easy to serve.
The marinade adds plenty of flavor. Whole-grain mustard, Dijon, honey, lemon, and garlic give the chicken a mix of tangy, sweet, and savory flavors.
Roasted peppers save preparation time. Jarred roasted red peppers are already soft and slightly sweet, so there is no need to cook them separately.
The almonds add texture. A small handful of toasted sliced almonds adds some crunch to the tender chicken and peppers.
I have made this casserole with both chicken breasts and thighs, but thighs work better for a relaxed Sunday dinner. They do not dry out as quickly, which helps when everyone is not ready to eat at exactly the same time.
Rice and roasted potatoes both work well on the side, although I usually add a simple salad too. The mustard sauce from the bottom of the dish is too flavorful to leave behind, so bread is also useful for soaking it up.
Key Ingredients Needed
Boneless chicken thighs: Chicken thighs stay tender during baking and absorb the mustard marinade well. Choose pieces that are similar in size so they finish cooking at the same time.
Whole-grain and Dijon mustard: Whole-grain mustard adds texture and a milder flavor, while Dijon gives the marinade a sharper taste. Using both creates a more balanced sauce.
Honey: A tablespoon is enough to soften the sharpness of the mustard and help the chicken brown in the oven.
Roasted red peppers: Jarred roasted peppers keep the preparation simple. Drain them well and cut them into strips before adding them to the casserole.
Lemon and garlic: Fresh lemon juice adds acidity, while garlic gives the marinade more depth.
Smoked paprika and oregano: These seasonings work well with the mustard and roasted peppers without making the dish spicy.
Sliced almonds: Toast the almonds briefly before adding them to the finished casserole. They can burn in the oven if added too early.
Fresh parsley or cilantro: Either herb adds freshness and a little color just before serving.
How to Make Baked Mustard Chicken Casserole
Make the mustard marinade. Whisk the olive oil, whole-grain mustard, Dijon mustard, honey, lemon juice, garlic, smoked paprika, oregano, salt, and black pepper in a small bowl.
Marinate the chicken. Place the chicken thighs in a large bowl and pour the marinade over them. Toss until every piece is coated, then cover and refrigerate for at least 30 minutes. You can also prepare the chicken in the morning and leave it to marinate for up to 8 hours.
Arrange the casserole. Place the marinated chicken in a lightly greased baking dish and pour any remaining marinade over the top. Drain the roasted red peppers well, slice them into strips, and scatter them around the chicken.
Bake the chicken. Bake uncovered at 400°F (200°C) for 25 to 30 minutes. The chicken is ready when the thickest part reaches 165°F (74°C).
Toast the almonds. Add the sliced almonds to a dry skillet over medium-low heat. Cook for 2 to 3 minutes, stirring frequently, until they are lightly golden.
Rest and serve. Let the chicken rest for 5 minutes, then sprinkle the toasted almonds and chopped parsley or cilantro over the casserole before serving.
Recipe Notes
Use similar-sized chicken thighs. Pieces of roughly equal size will cook at the same rate. If some are noticeably larger, cut them in half before marinating.
Give the chicken time to marinate. Thirty minutes is enough for the mustard, lemon, and garlic to flavor the chicken, but you can marinate it for up to 8 hours.
Drain the peppers well. Too much liquid from the jar can water down the mustard sauce at the bottom of the dish.
Check the internal temperature. Chicken thighs vary in thickness, so cooking time may differ slightly. The chicken is ready when the thickest part reaches 165°F (74°C).
Add the almonds after baking. Almonds can burn quickly in a hot oven. Toasting them separately keeps them crisp and gives you better control over the color.
Broil the chicken for more color. If it still looks pale after baking, place the casserole under the broiler for 2 to 3 minutes. Watch it carefully because the honey in the marinade can burn.
Let the chicken rest before serving. Five minutes gives the juices time to settle and allows the sauce to thicken slightly.
Prepare part of the recipe ahead. Marinate the chicken and slice the peppers earlier in the day. Arrange everything in the casserole dish shortly before baking.