Preheat oven to 375 degrees Fahrenheit.

Cook pasta shells according to directions on package (for pasta to be cooked in oven). Once pasta is cooked, rinse with cold water and set them on paper towel to dry.

Heat olive oil in a large skillet over medium-high heat. Add onions and green peppers and cook until tender.

Add black pepper, garlic powder, parsley and spinach to skillet. Cook for about 5 minutes.

In a large bowl combine Ricotta cheese, 1/2 cup mozzarella cheese and 1/4 cup Parmesan cheese.

Add vegetables to cheese and stir until combined.

In a 9 x 13 in. pan, add about 1/2 cup of pasta sauce to the bottom of the pan.

Stuff each pasta shell with vegetable/cheese mixture and place them open side up in pan.

Pour the remaining pasta sauce over the shells.

Sprinkle the remaining 1/4 cup mozzarella cheese and 1/4 cup Parmesan cheese on top of the sauce.

Cook for 30 minutes or until cheese is melted and shells are tender.