Preheat oven to 350 degrees.
Heat oil in a small Dutch over medium-high heat. SautÃ© onions, pepper and mushrooms in pan until softened. Add tomato sauce and crab and bring to a simmer.
Add cooked pasta and half of cheese to crab mixture, stirring to combine. Pour into an 8-inch-square baking dish coated with cooking spray and sprinkle with remaining cheese. Bake for 35-40 minutes or until bubbly.