Each year, thousands of pounds of morels are harvested in Oregon. In order to find them, however, a person needs to know when, how, and were to look.
The ‘when’ is easy. Morels are usually picked in May and June, before the onset of hot weather. Some morels may be found sporadically throughout the year, however this mushroom tends to follow the snow line as it melts, so when there is no snow and the temperatures have risen, there probably aren't going to be large numbers of morels.
How to find them won't be addressed here, as it is a separate topic of its own. There are some great resources for learning how to find them, however.
So, where, specifically in Oregon, would you be most apt to find morels? There are few areas, where morels won't grow, however the answer is mostly in coniferous forests, especially of pine and fir. Luckily, about half the state is covered with forests, and these are predominantly fir and pine.
This narrows the field down quite a bit, though it doesn't quite answer the question of where the best places are in Oregon to find morel mushrooms. Still, it does point out places that aren't likely to be very productive for these mushrooms, such as the Oregon high desert, and valley floors.
Running through the state like a backbone, are the Cascade Mountains. The altitude is higher, but it is a great place for pine, fir, and mixed forests to exist. Coincidentally, it is also a great place to find morels. These trees provide shelter for the developing mushrooms, and the needles and limbs provide nutrients a morel needs, to grow.
The first clue is then that morel mushrooms are more likely to be found in the Cascades. Again, this isn't very specific, however these places get large amounts of snow, and when it melts, it provides moisture even as the ground is warming up sufficiently for them to grow.
Morels are found along both the west and east slopes of the Cascades. Examples of 'hot' morel picking areas include all the way around the Crater Lake National Park boundary (picking morels inside the park is illegal), and near Lake of the Woods and Fish Lake, on Highway 140. Note that in both locations, the altitude is between 4,000 and 5,000 feet, or very close to it.
It relates to how to find morels in that morels need soil that at least partly dries out, but dirt that warms up sufficiently, and which has the right nutrients.
Armed with this information, you can find the best places in Oregon to find morel mushrooms. Once you find a lot of them and pay attention to what trees are present, what the altitude is, and what the soil condition is, it will make little difference if you are in the northern part of the state or the southern part, you will know the type of country and conditions to look for.