In a separate pan boil the green beans for a few minutes, drain and put in a bowl with the frozen peas and set aside
Heat the oil in a non-stick shallow pan
Add the garlic and onion and fry until softened
Add the pearl barley and rosemary and stir around to coat the grains
Add a little of the stock and stir until absorbed, repeat this until all of the stock is absorbed and the pearl barely is cooked (I like it with a little bite. If you prefer softer then add a little more water and continue to stir.
Finally add the green beans and the peas and continue to stir until warmed through