Preheat oven to 350°F Spray a 9 x 7 inch glass dish with cooking spray and set aside.
Cook the pasta shells according to package directions.
While the pasta is cooking, make the sauce: saute the garlic in olive oil in a medium saucepan; add all additional sauce ingredients and bring to a simmer; cook on low heat, stirring occasionally, until ready to assemble the shells.
Stir together all filling ingredients until well combined.
Drain the cooked pasta shells. Pour about 1/4 of the sauce in the bottom of the glass baking dish; fill each pasta shell with cheese filling, dividing evenly among the 12 shells.
Arrange shells in the baking dish and pour the remaining sauce over the top; sprinkle with parmesan cheese and oregano.
Cover with foil and bake for about 50 minutes; uncover and bake for another 5-10 minutes, or until parmesan cheese is lightly browned.