Where in the United States are you? It makes a difference if you are north, south, east, or west.
Because of limited sun grasses often have a difficult time growing where pines are, nothing to do with the needles.
What is the soil like in that area? Like all other plants grasses need a good, healthy soil to grow in and making that soil into that good, healthy condition will help some getting grasses to grow.

The soil under large trees is often too dry to grow grass due to the sheltering aspect and also because trees take all the moisture to grow. The soil is also often devoid of nutrients because the trees have taken it over years. One can replace the soil as much as possible and water but it's a continuing problem.

I have an island of spruce, fir, and aspen in my front yard and have amended the soil, planted shade plants on the north side and perennial ornamental grasses on the south side. Not a perfect solution but easier than trying to grow lawn grasses in a difficult situation. Every fall I rake the available leaves into that area and continue to amend the soil with whatever I can get and water as necessary.

Grass needs healthy soil?

provide enough water and you can grow turf on asphalt.

fescues are more shade tolerant.

what about a ground cover like vinca, pachysandra, hosta (a quick trip to insanity), or about a zillion others

The northeast. Lancaster County, PA.

Thanks for all the help!

Markus

Pine needles can have allelopathic affects on other plants, especially germinating seeds. Sometimes the best thing to have under pine trees is....pine needles. Best for the pines, too.

Jumpilot are they pine or are they spruce or fir...?

I have two spruce who make growing grass around the edge of their drip line a challenge but have found it is the shade more than anything that is causing grief.

I had a mulberry tree that had a horizontal branch shoot out over the boulevard under which grass was alway rather thin and sickly.
After cutting it off, no other changes, the grass greatly improved.

Back to what rhizo_1 said. Pines are allelopathic for a number of reasons. My question: how often do you see turf in a pine forest? Grass under pines is a difficulty, an uncooperative combo. Use other plant materials that are tolerant of the duff, acidity and shade, OR, pine duff. Pines are happy living with only their duff below.
hortster

Where the Red Pines in my windbreaks grow the grass on the south and west side grows really well, even with a fairly heavy layer of pine needles there, but the grass on the north side, shaded, does not grow well because of too little sunlight reaching that area, until several feet out where the sun does reach the grass. Some fescues do fairly well there in the shady areas, so possibly in Pennsylvania one of the fescues could be seeded there. even then getting the soil into a good, healthy condition will help. Like any other plant grasses will grow better in good, healthy soils, although some grass species only need a bit of soil and moisture to root in.

How about something besides grass. Because very few grasses can out-compete pine trees for water under the tree.

Find something that naturally grows under pines - shrubs, ferns, perennial flowers - and don't fight Mother Nature.

Lazy Gardens is right. Grass needs a lot of water. It would better to grown another nice sort of ground cover. If one was to rake up the pine needles and compost them in the bin instead of letting them stay there, it would be better for the ground cover plants. They make great compost. I like them because I want more acid soil. I know they can't make the soil acid, but adding acid things to my compost is a benefit in my soil.

Compost & coastal Bahia will do the trick.
But the grass may not stop at the edge of your beds