In a cast iron or heavy bottom skillet, heat 2 tablespoons olive oil and brown the pork on medium high heat until the sides of the meat have a caramel color. Do not overcrowd the pan; work in batches.
Add 2 more tablespoons of olive oil and saute the onions and peppers over medium high heat for about 10 minutes or until the onions are translucent and softened.
With a slotted spoon, strain and scoop out the onions and peppers and place them with the meat in the bowl of the slow cooker.
Add the Masa, stirring to combine and cook over medium heat for about 1 minute, stirring often.