Spray the inside of slow cooker with non-stick spray.
Combine cinnamon and sugar; sprinkle a small amount to cover the bottom of the slow cooker. Add apples and pears to slow cooker. Sprinkle remaining cinnamon sugar on top of the fruit.
In a large bowl, combine oats, flour, and brown sugar. Mix thoroughly. Use a pastry cutter or fork to cut the butter into the mixture until the mixture becomes crumbly. Sprinkle mixture over the fruit in the slow cooker.
Drape a layer of paper towels over the top of the slow cooker and then cover with lid. The paper towels will work to absorb extra moisture, to help give the crisp that “crispness”.
Cook on low for 2 hours. Allow to cool briefly before serving. Serve with ice cream, or whipped cream, if desired.