My guess- Oregon Grape Holly. (Mahonia Aquifolium).

not Mahonia of any type. Definately a type of Berberis (Barberry). Probably B. Darwinii

I agree with Berberis. I'm going to say Berberis darwinii-Barberry.
:)

Look in Wickipedia under Oregon Grape. It says some authors submerge "Mahonia" under barberries .

I've found one or two sites that are using Mahonia and Berberis interchangeably. I don't know if they should but these sites are stating we're both right. They are two seperate plants with Berberis having the common name of barberry and mahonia as being oregon grapes. Also some information classifies Mahonia as being in the same family as berberis. If you do a search berberis+flowers+photos I'm pretty sure you'll find it matches your photos. Don't forget to have a look at the buds. They're different. I think they interchange the names of these plants name too easily, maybe it's because the leaves look somewhat alike or even the flowers themselves, but they aren't the same. I still have to go with Berberis darwinii-Barberry and I still have to say they are different plants

That was quick! Those little flowers look like tiny roses. Beautiful plant Cassie

Looks like oregon grape to me, though the ones in my area have yellower flowers than those pictured. Oregon grapes form fruit clusters in the fall; the individual berries are about the size of blueberries and have the same color and dusty blush, but are much firmer. They're too bitter to make good eating, but boy do they make terrific jelly.
--Kate

Okay, I am hereby beating a full retreat: Sherryl is spot on about the search for berberis+flowers+photo. The two best sites I found are Plant Index for Mexico, the Pacific Northwest, and the USA Southwest at http://www.mailordertrees.co.uk/Berberis_darwinii_(Barberry).htm and a mail-order site at http://www.mailordertrees.co.uk/Berberis_darwinii_(Barberry).htm where the photo looks exactly like Cassie's.

The first of these sites gives oregon grape as Berberis Aquifolia, and both say that B.Darwinii (like Oregon grape) has edible berries (one site says blue, the other black) that are excellent in jams and jellies.