Melt coconut oil in a medium frying pan over medium heat. Once hot, add red curry paste and saute for one minute. Add a couple tablespoons of coconut milk and mix paste in until dissolved.
Add curry mixture, remainder of coconut milk, beef, and fish sauce into slow cooker. Stir well and cover.
Cook on LOW for 4 hours then add peas and sliced red peppers. Mix in and replace cover.
Continue cooking on LOW for 2 more hours, for a total cooking time of 6 hours.