High-Protein Chicken Casserole with Spinach & Sweet Potatoes

The ultimate weeknight warrior: a golden-topped, nutrient-packed casserole that lands on the table in under an hour and keeps the whole family happy.

Last Tuesday I walked through the door at 6:17 p.m. with a first-grader whose backpack was somehow sticky, a preschooler who had decided socks were optional, and a stomach that had been growling since the morning Zoom call. By 7:05 we were all sitting down to this bubbling beauty—tender cubes of chicken, silky sweet potatoes, and wilted spinach held together by a light, protein-boosted Greek-yogurt custard that tastes like comfort food but performs like a post-workout shake. My kids asked for seconds; my husband asked for the recipe card so he could make it for his next guys’ night (apparently “casserole” is no longer a four-letter word). If that isn’t a weeknight miracle, I don’t know what is.

I started developing this recipe after my annual January “let’s-eat-more-protein” pact. I wanted something that could be prepped while the oven preheated, didn’t require a sinkful of pots, and would still deliver 35+ grams of protein per serving. Twelve iterations later, this is the keeper: no precooking chicken, no wringing out spinach, no sad, watery sweet potatoes. Just one 9×13 dish, five minutes of whisking, and 35 minutes of hands-off oven time. It’s gluten-free, nut-free, and easy to make dairy-free if you swap the yogurt for coconut yogurt and skip the feta. I’ve served it to picky toddlers, macro-tracking CrossFit friends, and my mother-in-law who swears she “doesn’t eat healthy food.” They all clean their plates.

Why This Recipe Works

One-Pan Convenience: Everything bakes together—no stovetop precooking, no extra skillets to wash.
Protein-Packed Custard: Greek yogurt + eggs create a silky binder that adds 12 g extra protein per serving.
Fast Sweet-Potato Trick: Dice them small (½-inch) so they roast through in the same time the chicken cooks.
Veggie Boost Without Effort: Frozen chopped spinach goes in straight from the bag—no thawing or squeezing.
Customizable Seasoning: Use taco, Cajun, or Mediterranean spice blends to fit any craving.
Freezer-Friendly: Assemble, cover tightly, and freeze up to 3 months; bake from frozen 55-60 minutes.
Kid-Approved Texture: Soft cubes and cheesy top pass the “no weird chunks” test every time.

Ingredients You'll Need

Think of this ingredient list as a template: swap spices, swap veggies, but keep the ratios of protein : starchy veg : custard the same and the casserole gods will reward you.

Chicken breast – 2 lbs (about 900 g) trimmed and cut into ¾-inch cubes. I buy the family pack, trim it all at once, and freeze in recipe-ready portions. Thighs work too; just bump cook time by 5 minutes.

Sweet potatoes – 1½ lbs (680 g). Look for the orange-fleshed Garnet or Jewel varieties; they’re moister and sweeter than the tan-fleshed Japanese varieties. Peel if you want, but I leave the skin on for extra fiber—just scrub well.

Frozen chopped spinach – 10 oz bag. Frozen is picked and flash-frozen at peak ripeness, so it’s often more nutrient-dense than the “fresh” spinach that’s been riding in a truck for a week. Plus it’s already chopped and blanched—zero prep.

Greek yogurt – 1 cup plain 2 %. Full-fat will taste richer, 0 % will still set fine, but 2 % hits the creamy vs. macro sweet spot. If you’re dairy-free, use an unsweetened coconut yogurt with at least 6 g protein per serving.

Eggs – 3 large. They act as the custard’s “glue.” Room-temperature eggs whisk more smoothly; if you remember, pull them out 20 minutes ahead.

Feta or goat cheese – ½ cup crumbled. Salty, tangy pops that keep the casserole from tasting like “diet food.” Omit or use vegan cheese for dairy-free.

Low-sodium chicken broth – ⅓ cup. Adds moisture without calories and keeps the yogurt from curdling.

Spice blend – 1 Tbsp. I rotate between smoked paprika + cumin + chili powder (Southwest), Italian herb blend + lemon zest (Mediterranean), or Cajun seasoning (spicy). All are sensational.

Garlic powder & onion powder – 1 tsp each. Reliable flavor base when you don’t want to chop aromatics at 6 p.m.

Olive oil – 2 Tbsp. Helps the sweet potatoes caramelize and keeps the chicken juicy.

Sea salt & black pepper – 1 tsp salt and ½ tsp pepper to start; adjust at the table.

Optional topping – ⅓ cup shredded mozzarella or ¼ cup panko mixed with 1 Tbsp everything-bagel seasoning for crunch.

How to Make High-Protein Chicken Casserole with Spinach & Sweet Potatoes for Weeknights

Preheat & Prep Pan

Position rack in center of oven; preheat to 425 °F (220 °C). Lightly grease a 9×13-inch ceramic or glass baking dish with olive oil or non-stick spray. Ceramic retains heat gently and prevents the bottom from scorching—worth the extra dollar.

Season the Chunks

In the prepared dish, add chicken cubes and sweet-potato cubes. Drizzle with olive oil, sprinkle spice blend, garlic powder, onion powder, salt, and pepper. Toss with your hands (fastest) until every piece is slick and speckled. Spread into a single layer; tuck spinach evenly over the top—no need to stir it in, it will wilt and sink as it bakes.

Whisk the Custard

In a 4-cup measuring jug (less washing) whisk Greek yogurt, eggs, and broth until smooth and no white streaks remain. Pro tip: tap the jug on the counter a few times to pop bubbles; this keeps the top of the casserole satin, not cratered.

Pour & Sprinkle

Slowly drizzle custard over the casserole; shimmy the pan so it seeps into every crevice. Scatter feta evenly, then add optional mozzarella or panko topping. Press lightly so the cheese adheres but doesn’t sink.

Bake Uncovered

Slide onto the center rack and bake 30 minutes. Rotate pan 180 ° for even browning; bake 5–8 minutes more, until the top is spotty golden and the internal temp of the chicken hits 165 °F (74 °C). Broil 1–2 minutes for extra blistered cheese—watch like a hawk.

Rest & Serve

Let stand 5 minutes. The custard firms as it cools, giving you picture-perfect squares. Spoon onto plates and finish with chopped parsley, a squeeze of lemon, or a drizzle of sriracha if you like heat.

Expert Tips

Temp Check Trick

Insert your instant-read into the thickest chicken cube through the custard; you want 165 °F. If the top is browning too fast, tent loosely with foil and continue baking until temp is met.

Overnight Flavor Boost

Assemble the night before; cover tightly with plastic wrap and refrigerate. The spices penetrate the chicken so the finished dish tastes like it marinated for hours.

Speed Dicing

Cut sweet potatoes into ½-inch cubes: first slice lengthwise into ½-inch planks, stack, slice into sticks, then crosswise into cubes—uniform size = uniform cooking.

Macro Balance

Each serving clocks 38 g protein, 32 g complex carbs, 10 g fat. Want leaner? Skip the cheese topping; want more carbs? Stir in ½ cup rinsed quinoa—add ¼ cup broth.

Crusty Edge Hack

If you live for those caramelized edges, use a metal pan and position 1 rack notch lower; metal conducts heat faster, creating more surface browning.

Left-Wild Remix

Tomorrow, stuff leftovers into whole-wheat tortillas with salsa for 2-minute quesadillas, or mash into lettuce cups for a 100-calorie snack.

Variations to Try

Mediterranean: Swap cumin for oregano + lemon zest, add ½ cup sun-dried tomatoes, and top with kalamata olives.
Buffalo-Ranch: Replace spice blend with 2 Tbsp Frank’s RedHot + 1 tsp ranch seasoning; serve with a light blue-cheese drizzle.
Vegetarian: Sub 2 cans chickpeas (rinsed) for chicken; reduce bake time to 25 minutes.
Low-Carb: Replace sweet potatoes with 2 medium heads cauliflower cut into small florets; add 2 Tbsp olive oil to keep them moist.
Tex-Mex Quinoa: Add ½ cup rinsed quinoa + ¼ cup broth; use taco seasoning + corn kernels; top with pepper-jack.
Green Goddess: Blend ¼ cup fresh basil, 2 Tbsp parsley, and 1 Tbsp chives into the yogurt custard for a spring-green hue and herbaceous punch.

Storage Tips

Refrigerate: Cool completely, slice into squares, and store in an airtight container up to 4 days. Reheat single portions in the microwave 60–90 seconds, or warm the entire dish covered at 350 °F for 15 minutes.

Freeze: Wrap individual squares in plastic wrap, then foil; freeze up to 3 months. Thaw overnight in the fridge or microwave straight from frozen 2–3 minutes, flipping halfway.

Make-Ahead: Assemble through Step 4, cover tightly, and refrigerate up to 24 hours. Add 5 minutes to bake time if starting cold.

Meal-Prep: Double the batch, bake in two pans, and you’ve got eight grab-and-go lunches. Add a side salad or microwave-steamed broccoli for a full plate.

Frequently Asked Questions

Yes—use 6 packed cups raw spinach. Roughly chop, then wilt in the microwave 45 seconds; squeeze dry so excess water doesn’t dilute the custard.

Likely cut too large or your oven runs cool. Dice ½-inch max, and check oven calibration with an inexpensive oven thermometer.

Not recommended—the custard needs dry heat to set. Slow cookers create steam, so you’d end up with watery chicken soup.

Not as written—sweet potatoes add 18 g net carbs per serving. Use cauliflower for a keto version (6 g net carbs).

Give the pan a gentle jiggle; the center should wobble slightly but not ripple like liquid. A toothpick inserted should come out mostly clean—think cheesecake, not cake.

Absolutely—use two 9×13 pans and bake on the middle and lower racks; swap positions halfway. Total bake time stays the same.

highprotein chicken casserole with spinach and sweet potatoes for weeknights

High-Protein Chicken Casserole with Spinach & Sweet Potatoes

Why This Recipe Works

Ingredients You'll Need