This website says the following vegetables contain high protein "Beans of all kinds, lentils, asparagus, broccoli, seaweeds; variety is important and quantity." http://wiki.answers.com/Q/
Eggs and yogurts can be good sources of protein too. http://www.weightlossforall.
"Spinach is an inexpensive vegetable that contains protein and carbohydrates. According to The Daily Plate, 4 cups of spinach contain 3 g of carbohydrates and 2 g of protein. Because spinach contains 20 calories per serving, it may be an effective source of protein and carbohydrates for dieting. Spinach contains 2 g of fiber per serving, which promotes feelings of fullness. In addition, spinach contains vitamins A and C, folic acid and magnesium, among other nutrients."