Absolutely!
funnily, I find it easier to paint in oil colours plein air. I tend to use the Griffin Alkyds, they are smaller tubes and I buy the great big tubes of normal oils - toooo heavy! they have the advantage of drying overnight as well.
I either paint on paper in my sketchbook or use a pad of cryla paper (designed for acrylics but great with oils as well) You can shut the book without damaging the painting and work on the next page with no problem. the oils don't leak through.
With oils you can work backwards and forwards, scratching through and putting light on top of dark and it's more forgiving than watercolours - though I do sometimes use them plein air but more often as mixed media with oil pastels or pastels and pen and everything but the kitchen sink added
I find that a plastic box with the paints, a small bottle of turps/white spirit, a bottle of baby oil (for cleaning me and brushes), some rags, a couple of brushes and a palette knife and palette is enough.
If you haven't painted plein air before it might seem difficult at first but stick with it. You'll learn so much about colour and atmosphere and it'll feed into your other work.
I've got a new website and you can see some of the stuff on there - if you are interested I can pm the address.
Enjoy
and post the results? build a website for them?