Cheesy Ground Beef Fajita Casserole
Skillet fajitas in a baking dish – peppers, mushrooms, and a long cheese pull
This is fajita night without the tortillas. Ground beef gets a hard brown, then peppers, onion, and mushrooms cook in the same skillet with cumin, chili, and paprika. Everything goes into a glass dish, cheese goes on top, and you pull a stretchy slice about 40 minutes after you start.
No flour, no rice. The peppers do the work. Rest it 5 minutes so the spoon comes out stacked.
Why you’ll love this casserole
- 38g protein per serving – a real dinner, not a side
- Only 7g net carbs – peppers instead of tortillas
- One skillet plus one dish, about 40 minutes
- Melted cheese pull with browned beef and sweet peppers
- Reheats well for meal-prep lunches
- Tastes like fajitas without the wrap
Health notes
- High protein: Beef plus a full cheese lid.
- Low carb: Bell peppers and mushrooms, no rice or tortillas.
- Peppers: Color, crunch, and vitamin C with very few carbs.
- No flour: The skillet and a short rest set the layers.
Key element – brown the beef hard, keep the peppers crisp-tender
Give the beef real color before you add anything wet. Then cook the peppers just until they soften at the edges. If they go limp in the skillet, they turn soggy in the oven. You want ribbons that still hold a bite under the cheese.
Ingredients
Beef and fajita mix
- 1 1/2 lb (680g) lean ground beef (90/10 or 93/7)
- 1 small onion, sliced thin
- 1 red bell pepper, sliced
- 1 yellow bell pepper, sliced
- 1 green bell pepper, sliced
- 8 oz (225g) mushrooms, sliced
- 3 garlic cloves, minced
- 2 Tbsp olive oil, divided
- 1 1/2 tsp chili powder
- 1 tsp ground cumin
- 1 tsp smoked paprika
- 1/2 tsp dried oregano
- 3/4 tsp salt + 1/2 tsp black pepper
- 2 Tbsp tomato paste
- 1/4 cup beef broth or water
- Juice of 1/2 lime
Cheese lid
- 1 1/2 cups shredded mozzarella
- 3/4 cup shredded cheddar or Mexican blend
- Chopped cilantro or parsley to finish
Swaps
- Turkey: Use ground turkey and add 1 Tbsp oil so it does not dry out.
- Spicy: Add sliced jalapeno with the peppers or a pinch of cayenne.
- Creamy: Stir 2 oz cream cheese into the skillet before you transfer.
- No mushrooms: Add extra peppers or a handful of zucchini strips.
Instructions
| 1 | Heat the oven. Heat oven to 375 F (190 C). Lightly grease a 9×13-inch glass baking dish. Slice the peppers, onion, and mushrooms so they are ready when the beef is browned. |
| 2 | Brown the beef. In a large skillet over medium-high, heat 1 Tbsp oil. Cook the beef until well browned, 6 to 8 minutes. Drain extra fat. Stir in chili powder, cumin, paprika, oregano, salt, and pepper 30 seconds. |
| 3 | Cook the fajita veg. Push beef to the side or transfer it to a bowl. Add remaining oil, onion, peppers, and mushrooms. Cook 4 to 5 minutes until the peppers are just tender at the edges. Stir in garlic 30 seconds. |
| 4 | Sauce and layer. Stir beef back in with tomato paste, broth, and lime. Simmer 1 to 2 minutes until thick, not soupy. Spread in the baking dish. Top with mozzarella and cheddar. |
| 5 | Bake and rest. Bake 20 to 25 minutes until the cheese is melted, bubbling, and browned in spots. Rest 5 minutes. Garnish with cilantro and serve with extra lime if you like. |
Pro tips
- Slice peppers into long strips so they look like skillet fajitas, not diced salad.
- Do not crowd the skillet or the veg steams. Work in two batches if needed.
- The mix should mound on a spoon before it goes in the dish. Thin sauce = watery bake.
- Resting is not optional. Five minutes lets the cheese set so the spoon lifts a stack.
- If the top browns too fast, tent loosely with foil for the last 5 minutes.
Nutrition
| Nutrient | Per serving (1/6) |
|---|---|
| Calories | 420 |
| Protein | 38g |
| Net carbohydrates | 7g |
| Total carbohydrates | 10g |
| Fiber | 3g |
| Total fat | 26g |
| Sodium | 680mg |
Estimates with 90/10 beef and a full cheese lid. Pepper size and cheese brand will shift the numbers.
Variations
Taco night
Use taco seasoning instead of the spice mix. Finish with cilantro and a dollop of sour cream.
Steakhouse
Swap half the beef for leftover sliced steak. Add extra mushrooms.
Green chile
Stir in a small can of diced green chiles with the tomato paste.
Meal-prep cups
Divide into 6 ramekins and bake 15 to 18 minutes. Easy lunch boxes.
Storage
| Method | Time | Notes |
|---|---|---|
| Refrigerator | Up to 4 days | Covered; reheat at 350 F or in the microwave |
| Freezer | Up to 2 months | Cool fully, wrap well; thaw overnight |
| Meal prep boxes | Up to 4 days | Drain any extra liquid before packing |
FAQ
Test your knowledge
5 quick questions about this casserole
1. Protein per serving?
2. Net carbs per serving?
3. Oven temperature?
4. How long should the peppers cook in the skillet?
5. What replaces tortillas here?
