Millet? In new grass
It looks from your photo that you have crabgrass. Crabgrass is not a big problem in Oregon but it can come up with summer plantings or in thin grass stands on south facing slopes. It will die once the first frost comes. Crabgrass generally germinates in Oregon around the first week of April if the area is in full sun, later if it is not as warm. However, if you keep your lawn dense, you will likely not have a problem next year.
If you want to get rid of it now, you can spray Drive XLR8 with methylated seed oil, but you need to wait until 4 weeks after the grass seedlings have emerged or else it will damage your lawn. Assuming you get the rate correct, you can spray Drive XLR8 + methylated seed oil over your entire lawn and it will kill the crabgrass, but not the lawn. Read the label and carefully follow the instructions, or hire a licensed pesticide applicator. The problem most people have is that they do not have a sprayer to make the application uniformly. Alternatively, you could spot spray the crabgrass but you need to make sure you get the rate correct which can be difficult with a backpack sprayer. But if you get the rate wrong, you are not killing your entire lawn. With a backpack, you want to assume 1 gallon of water or spray solution sprays 1,000 sq. ft. for mixing purposes, and only spray over the crabgrass plant 1 time.
Additionally, if you want to be sure that you do not get crabgrass next summer, you can spray a pre-emergent herbicide next March. In fact, applying pre-emergent herbicides are the most effective way of dealing with crabgrass. Some common pre-emergent herbicide options for this purpose include Dimension, Barricade, and Pendulum Aquacap. The pre-emergent herbicides should be watered in after the application. Drive XLR8 should not be watered in - it needs to dry on the leaf so do not apply before expected rain.
My recommendation would be to wait for the crabgrass to die from frost, seed any bare spots again now and keep your lawn dense next spring and see how big a problem you really have. If you get a lot of crabgrass next year, then apply Drive XLR8 + methylated seed oil immediately before the grass flowers. If I have a big problem next year, the following year, I would apply a pre-emergent herbicide in March and that should take care of your problem.