Slow Cooker Stuffed Bell Peppers with Mozzarella

Quick Recipe Version (TL;DR)

• Yield: 6 stuffed peppers (6 servings)
• Prep Time: 25 minutes
• Cook Time: 6 hours 10 minutes on LOW (or 3 hours 10 minutes on HIGH)
• Total Time: 6 hours 35 minutes on LOW (or 3 hours 35 minutes on HIGH)

Quick Ingredients

• 6 medium bell peppers
• 1 lb ground beef (85–90% lean)
• 1 small onion, finely diced
• 3 garlic cloves, minced
• 1 cup cooked long-grain white rice (cooled)
• 1 can (14.5 oz) diced tomatoes, drained
• 2 tbsp tomato paste
• 1 tbsp Worcestershire sauce
• 2 tsp Italian seasoning, divided
• 1 1/2 tsp kosher salt, divided
• 1/2 tsp black pepper
• 1/4 tsp crushed red pepper flakes (optional)
• 1 can (15 oz) tomato sauce + 1/2 cup low-sodium beef broth
• 1 1/2 cups shredded mozzarella
• 2 tbsp chopped fresh parsley
• 1 tbsp olive oil

Do This

• 1) Prep peppers: slice off tops, remove seeds/membranes, trim bottoms only if needed to sit upright.
• 2) Brown: in 1 tbsp oil, cook beef and onion 5–6 minutes; add garlic 30 seconds; drain fat.
• 3) Mix filling: stir in rice, drained tomatoes, tomato paste, Worcestershire, 1 1/2 tsp Italian seasoning, 1 tsp salt, pepper, red pepper, and parsley.
• 4) Sauce base: in slow cooker, combine tomato sauce, broth, 1/2 tsp Italian seasoning, 1/2 tsp salt; nestle peppers upright.
• 5) Stuff peppers; spoon a little sauce inside each. Cook 6 hours on LOW or 3 hours on HIGH, until tender and filling reaches 160°F.
• 6) Top with mozzarella; cover 10–15 minutes to melt. Garnish with parsley and serve with the sauce.

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Why You’ll Love This Recipe

• Set-it-and-forget-it comfort food with a classic Italian herb aroma.
• Balanced and satisfying: savory beef, tender peppers, and melty mozzarella.
• Great for meal prep and freezes beautifully.
• Foolproof for busy weeknights or casual company.

Grocery List

• Produce: 6 bell peppers, 1 small yellow onion, 3 garlic cloves, fresh parsley
• Dairy: Shredded low-moisture mozzarella
• Pantry: Ground beef, long-grain white rice, canned diced tomatoes, tomato paste, tomato sauce, low-sodium beef broth, Worcestershire sauce, Italian seasoning, kosher salt, black pepper, crushed red pepper flakes, olive oil, sugar (optional)

Full Ingredients

Peppers

• 6 medium bell peppers (any colors), tops sliced off, seeds and membranes removed

Filling

• 1 lb (450 g) ground beef, 85–90% lean
• 1 tbsp olive oil
• 1 small yellow onion, finely diced (about 3/4 cup)
• 3 garlic cloves, minced
• 1 cup cooked long-grain white rice, cooled (about 1/3 cup raw rice before cooking)
• 1 can (14.5 oz/411 g) diced tomatoes, well drained
• 2 tbsp tomato paste
• 1 tbsp Worcestershire sauce
• 1 1/2 tsp Italian seasoning
• 1 tsp kosher salt
• 1/2 tsp freshly ground black pepper
• 1/4 tsp crushed red pepper flakes (optional)
• 2 tbsp fresh parsley, chopped

Sauce (for the slow cooker)

• 1 can (15 oz/425 g) tomato sauce
• 1/2 cup low-sodium beef broth
• 1/2 tsp Italian seasoning
• 1/2 tsp kosher salt
• 1/2 tsp sugar (optional, to balance acidity)

Finish

• 1 1/2 cups shredded low-moisture mozzarella (about 6 oz)
• Extra chopped parsley, for garnish

Step-by-Step Instructions

Step 1: Prep the peppers

Slice about 1/2 inch from the tops of the bell peppers and remove seeds and membranes. If a pepper wobbles, shave a tiny sliver off the bottom so it stands upright without cutting through the cavity. Rinse and pat dry. Set aside while you start the filling.

Step 2: Make the sauce base in the slow cooker

In a 5- to 6-quart slow cooker, stir together the tomato sauce, beef broth, 1/2 tsp Italian seasoning, 1/2 tsp kosher salt, and sugar (if using). Spread the sauce into an even layer. This flavorful base will gently braise the peppers and keep them moist.

Step 3: Brown the beef and aromatics

Heat 1 tbsp olive oil in a large skillet over medium-high heat. Add the ground beef and diced onion. Cook, breaking up the meat with a spoon, until the beef is no longer pink and the onion is translucent, 5–6 minutes. Add the minced garlic and cook 30 seconds more, just until fragrant. Drain off excess fat.

Step 4: Build the savory filling

Off the heat, stir in the cooked rice, drained diced tomatoes, tomato paste, Worcestershire sauce, 1 1/2 tsp Italian seasoning, 1 tsp kosher salt, black pepper, crushed red pepper flakes (if using), and 2 tbsp parsley. Mix until evenly combined; the mixture should be moist and cohesive but not soupy.

Step 5: Stuff and nestle the peppers

Spoon the filling into each pepper, pressing lightly to remove air pockets and filling to just below the rim. Nestle the stuffed peppers upright into the sauce in the slow cooker. Spoon a tablespoon of sauce into the top of each pepper.

Step 6: Slow cook until tender

Cover and cook on LOW for 6 hours or on HIGH for 3 hours, until the peppers are tender when pierced with a knife and the center of the filling registers 160°F. Avoid lifting the lid during cooking to retain heat. For crisper peppers, begin checking at 5 hours on LOW or 2 1/2 hours on HIGH.

Step 7: Finish with mozzarella and serve

Sprinkle the mozzarella evenly over the tops of the peppers. Cover and cook 10–15 minutes, until the cheese is fully melted and glossy. Spoon the warm tomato sauce from the cooker around and over the peppers. Garnish with extra parsley and serve hot.

Pro Tips

• Choose peppers of similar size so they cook evenly; mixed colors make a beautiful presentation.
• Drain the diced tomatoes well to keep the filling from becoming watery.
• Gently pack the filling—too tight and it can cook dense; too loose and it may dry out.
• Resist opening the lid; every peek can add 20–30 minutes to the cook time.
• For a browned, bubbly top, transfer cooked peppers to a broiler-safe dish and broil 2–3 minutes before serving.

Variations

• Turkey & Herb: Swap beef for lean ground turkey and add 1 tsp lemon zest with the parsley.
• Beef & Sausage: Use 1/2 lb beef + 1/2 lb mild Italian sausage; skip the Worcestershire and add 1/2 tsp fennel seed.
• Low-Carb: Replace rice with 1 1/2 cups riced cauliflower (no broth changes needed); reduce cook time by about 15 minutes.

Storage & Make-Ahead

Refrigerate cooled stuffed peppers in an airtight container up to 4 days. Reheat covered at 350°F for 20–25 minutes, or microwave 2–3 minutes per pepper until hot. Freeze individually wrapped peppers (without cheese) up to 3 months; thaw overnight, reheat as above, then add mozzarella and melt 10–15 minutes in the slow cooker or 5 minutes in the oven. The filling can be made 2 days ahead and refrigerated; stuff peppers just before cooking.

Nutrition (per serving)

Approximate: 370 calories; 22 g protein; 18 g carbohydrates; 22 g fat; 3 g fiber; 820 mg sodium. Values will vary based on brands and exact ingredients.