How can I make whole wheat bread and biscuits with out the bitter taste?

Part of the problem is that whole wheat flour goes rancid pretty quickly after it's milled (I believe it's from the natural oils in the germ). The usual advice is that whole wheat flour has a shelf life of six months or so, much less than white flour. If you're using old flour, try getting fresher stuff.

If you're willing to go through extra effort, consider milling your own whole wheat flour; after reading this article: http://www.realbakingwithrose.com/2006/11/rose_levy_beranbaums_100_whole.html I got a grain mill attachment for my KitchenAid mixer and started milling flour, and I've become a total convert. Fresh-milled whole wheat flour has an incredible taste. My standard loaf these days is 50% whole wheat and 50% bread flour, and it tastes great. It has a nice nutty flavor without the tree bark or cardboard you'd normally associate with bread with so much virtue in it. I've done 100% whole wheat loaves before, and while they're very good, they're just not my thing.

If you want to get even further into it, Peter Reinhart has a book on whole-wheat bread making, which has special starter techniques to get the best flavor possible. I realize your question is about biscuits and not necessarily bread, and his book doesn't have anything to say about biscuits or quick breads.

Much of the bitter taste in whole wheat products is a result of the hard red wheat used. In the last few years more companies like Bob's Red Mill, King Arthur Flours, and other have started distributing whole version of hard white wheat. A simple way to reduce the bitter flavor without decreasing the overall nutritional benefit of eat whole grain bread is to substitute whole white wheat for some of the traditional whole wheat called for in the recipe. White wheat has less protein than red wheat so you may need to add vital wheat gluten to achieve the same texture if you recipe is for a rustic-style hearth bread; if you are making a softer style bread additional gluten may not be necessary. For biscuits softer (lower protein) flour is often preferred, so no additional gluten should be needed.

I bake only whole wheat bread was disappointed with the lack of wheat flavor. After experimenting I find that the best way to develop the rich flavor is to use only a very small amount of yeast but let it rise cool and slow - using the freshest flour that I can get from my food co-op (that takes care of the bitterness)

For a 4 large loaf batch I'll make up the dough in the evening using 16 cups of flour but only 1 t yeast. For most of the year my kitchen is in the 60 68° range. In the morning I punch it down, knead it well, form it into balls for the bread pans, let it rise until double and bake it.

I think the long time the yeast has to digest the wheat also contributes to reducing bitterness.

My family has a 100% whole wheat bread recipe that tastes delicious. We use red whole wheat, but we also add a few tablespoons of honey and a tiny bit of stevia powder. If you don't want the extra sugar, maybe just try using the stevia. Not enough to make the whole bread very sweet, bust just enough to offset the bitterness.