Place spinach, zucchini, bell peppers and shrimp, in that order, in a steamer basket. Set in a saucepan over 1 inch (2.5 cm) of boiling water. Cover and steam until vegetables are tender-crisp and shrimp are cooked through, about 4 to 6 minutes.
Meanwhile, in a blender, combine and purée basil, lemon juice, salt and pepper.
In a large bowl, combine basil dressing with beans and shrimp.
To serve, divide vegetables among 4 plates. Top with shrimp and beans.