bending

I am new to learning dressage (been learning it all this year) and so is my horse that I have owned for three months. I have weekly lessons with dressage instructor. We are making huge strides in many areas but bending seems to be an obstacle. My horse is a quarter horse/Aus. stock horse and she seems to find bending quite difficult. What exercises are there that can help me work on this with her. I recently bought a book of dressage exercises and it includes some stretches to do from the ground. I did these with her today and for a couple of the stretches she could not bend very far so I will continue working on these more. What can I do in the saddle to help her bend properly around a circle. I did some leg yielding with her today and she eventually got the right bend for doing that for 2 or 3 strides at a time. is this a useful exercise?

Spiraling in and out of a circle, serpentines (15-20m loops), transitions on a large circle (20m), forward and back on a large circle.
As far as for leg yeilding, all it really does is help to begin the lateral aid connection (inside leg - outside rein), make sure you are keeping the neck coming straight out of the shoulders, keep the shoulder "leading" by keeping your outside leg back and use more outside rein than inside rein, try to keep very minimal flexion.
Once your horse gets this down, very good bending exercises to begin working on are shoulder in and travers. Start in the walk and don't ask for even three tracks of angle. Remember that in the shoulder in, they haunches stay traveling straight (the hind legs do not cross) and in the travers the forehand stays straight (the front legs do not cross and the ears stay pointing straight ahead).
Keep working under an instructor and hopefully they will be able to keep you doing these exercises correctly.

circle, push your horse into your outside hand/leg, and keep steady contact on your outside. its very hard at first for some horses. make sure to mix it up so the horse isnt doing circles for an hour. it comes with time and practice.

I don't do dressage. Sorry, lol. But I still like making sure Atty can bend. I usually do it as a warm up. Anyways, back to your question! I do serpentines, figure 8's, circles, and a loopy B thing. Works pretty well for me.

Just what exercises are you doing and just what are you referring to as bending ?

Many get bending and flexing confused so a more detailed explaination would be helpful.

I am referring to bending around my inside leg from ear to tail, enough to see the inside eye and nostril. My horse finds this quite difficult to do and after doing a good bend for a couple of strides will sometimes then swing her hindquarters out. I have tried to counter this by keeping my outside leg behind the girth but it hasn't been working very well. Is it just lack of strength and supplenes? Yesterday I feel like a I did a lot of good work with her and will continue the exercise I was doing plus incorporate some of what you guys here have said. Yesterday I did walk/trot transitions on a circle, trot/halt/trot transitions on a circle, leg yielding, walk/halt/rein-back transitions, bending from side to side whilst halted. I have tried serpentines in the past and will continue working on these and I will also try the spiral exercise. I also lunged her before I rode with lots of changes of direction and also over a couple of poles.

I have posted this video several times. mainly because the exercise that Phillippe Karl is doing is MY warm up when I ride. You may not get this good right away but if you worked like this on the beginning of every ride....improvement will show.

Wow he had a very nice counter bend!