Prepare noodles according to package instructions.
While noodles are cooking, heat 2 Tbsp. olive oil in a large skillet over medium-high heat.
Add halved peppers and sausage pieces and saute 10 minutes, stirring occasionally.
Add grape tomatoes and walnuts and saute 2 more minutes. Remove from heat.
Drain noodles.
In a separate container with a lid, combine 3/4 c. olive oil, lemon juice, garlic, oregano, salt & pepper. Shake vigorously to combine.
Toss noodles with olive oil mixture; top with peppers & sausage.
Crumble feta cheese on top and sprinkle with green onions.