Spray slow cooker with cooking spray.
Rinse quinoa well, using a fine mesh sieve. (Skip this step if you bought pre-rinsed quinoa)
Combine all ingredients except garnishes in slow cooker, stir well to combine.
Set on high for 2-3 hours, stirring after an hour and a half so you know how much longer to cook it. This will depend on how hot your slow cooker gets. (See note below.)
Oats are finished when they reach the consistency you desire - I like mine to still be slightly chewy, so I cooked mine for just over 2 hours.
Turn off heat and serve topped with dried cranberries, sliced almonds, extra brown sugar, or whatever you like!