Whisk the eggs and milk together in a jug and season.
Oil the inside of the ceramic slow cooker lot to prevent sticking. Alternatively you could line the pot with baking parchment.
Place the onion and pepper in the pot and pour over the egg mixture. Slice the goats cheese and place the pieces on the top, pressing them in slightly. Place the fresh rosemary sprigs on top.
Cook on high for approx 1 hour to 1.5 hours or until the edges of the frittata are brown and the eggs are all cooked through. I used a skewer to test the centre.
Cut the frittata in half with a knife and use a fish slice to remove the two halves of the frittata from the pot. Or, if you lined the pot with baking parchment, lift it out.
Serve with a green salad and crusty bread.