In large pot, heat oil over medium heat. Add onion; reduce heat to low, cover; cook for 6 minutes, stirring occasionally, until soft. Stir in beef; cook, stirring occasionally breaking beef apart, until browned. Stir in pasta sauce and tomatoes. Cover; simmer for 10 minutes, stirring occasionally.

Spread 2 cups (500 mL) of the sauce in the bottom of 13- x 9-inch (3 L) baking dish. Arrange one-third of the ravioli, in rows, in single layer over sauce, slightly overlapping edges. Top with 2 cups (500 mL) of the sauce, ensuring to cover pasta edges. Sprinkle with 2/3 cup (150 mL) of the cheese. Repeat with another 2 layers. Cover with foil sprayed with nonstick spray. Bake in 350°F (180°C) oven for 30 minutes. Remove foil; bake 10 minutes. Remove from oven. Let stand 10 minutes. Sprinkle with parsley.

Tip: Can be made ahead, covered, and refrigerated for up to 1 day. Add 15 minutes to the baking time.