Heat a large saucepan over a medium heat and add the oil.
Soften the onions and garlic for 2-3 minutes.
Add in all the other ingredients (except the peas).
Cover, and simmer for 15-20 minutes until the vegetables are soft.
You may need to simmer uncovered if it's looking a bit watery.
Towards the end, add the peas and cook for a further 2 minutes.
Delicious as a simple supper on its own, topped with white fish, or with prawns stirred in.