Preheat the oven to 200ºC.
Place the peppers (skin side up), onion, tomatoes and garlic on a baking sheet (you may need to use 2 trays) and roast in the oven for 30 minutes, until the peppers are soft and have charred.
Put all the roasted vegetables and all remaining ingredients, except the feta, into a large saucepan with the stock.
Stir well and bring to a boil, then reduce the heat and allow to simmer uncovered for 15 minutes.
Remove from the heat, stir through half of the feta and, using a stick blender, blitz until smooth, being careful not to splash yourself with hot soup!
Ladle into warmed bowls and sprinkle a little feta on top, along with some fresh herbs if you wish.