Heat oven to 350°F. Spray shallow 2 1/2-quart casserole with cooking spray.
In medium bowl, mix flour, brown sugar, pecans, butter and cinnamon until blended. In large bowl, mix sweet potatoes, vanilla and 1/2 cup of the streusel mixture. Spoon sweet potato mixture into casserole; sprinkle with remaining streusel mixture.
Bake uncovered 45 minutes or until thoroughly heated and streusel is crisp.