Preheat your oven to 200°C/Fan 180°C/Gas 6. Halve the pointed peppers and scoop out the seeds and white bits. Slice the peppers into strips roughly 1-2cm thick. Peel the red onions and cut them into thin wedges.
Scatter the peppers and onions into a roasting tin and toss with 1 tbsp olive oil and a pinch of salt and pepper. Slide the veg into the oven to roast for 20-25 mins, till softened and charred.
Meanwhile, drain and rinse the beans. Shake them dry and tip into a salad bowl. Peel the garlic and grate it into the bowl. Pick the oregano leaves and add them to the bowl. Pour in 1 tbsp each cider vinegar and olive oil. Add a pinch of salt and pepper and stir to mix.
When the peppers and onions are roasted, add them to the salad bowl. Fold through the lamb's lettuce. Divide the salad between a couple of warm plates, crumble over the feta and serve.