- Preheat oven to 400°F.
- Heat oil in large skillet on medium-high heat. Add sausage; cook 4-5 min. or until no longer pink, breaking up any large pieces. Add onions; cook 2-3 min. or until translucent, stirring frequently. Remove from heat; stir in sauce. Cool slightly.
- Cut stems off zucchini and slice lengthwise into ¼-inch-thick planks to yield about 15 slices. Working in batches, place zucchini slices in single layer on microwaveable plate lined with a double layer of paper towels. Microwave on HIGH 2 min.; pat dry.
- Combine Ricotta, Parmesan, egg, oregano and 1 cup shredded cheese in bowl until well blended.
- Arrange 5 zucchini slices on bottom of 8x8-inch baking pan. Top with half the cheese mixture and 1 cup sauce mixture; repeat layers. Top with remaining zucchini, sauce and shredded cheese. Cover tightly.
- Bake 30 min. or until edges begin to bubble. Uncover and broil 3-5 min. or until cheese is golden brown.
Tips: Substitute yellow squash for the zucchini, or use a combination of both squash and zucchini for additional color. This lasagna can be assembled up to 1 day ahead of time. Cover tightly and refrigerate. When ready to serve, add an additional 10 min. to the bake time.