A wide zigzag should be fine.

My vintage machine didn't have the option but my modern machine has the serpentine stitch Tartan mentioned. One of my friends does almost all her donation quilts with it, and somehow it works with each of them.

Here's my first attempt. I find it works very well for large grid patterns and will use again. The serpentine does a couple of stitches before moving over, the wide zig zag will be a slightly different look.

Edit: Do a test or two first looking at the thread color. You probably don't want it to look like a surgical scar! When in doubt, or with scraps, beige and grey threads can usually work without being too obvious.

I had attened my local quilt show last year and quite a few of the quilts displayed were quilted with a zig zag stitch. I think it added to the uniqueness (sp?).

I like to use a gentle serpentine stitch instead of a zig-zag. When I first started quilting, I used a zig-zag and when I washed the quilt, the ditch where the zig-zag was, was pretty visible as it had flattened out the area and I did not like the look.....if I had used a narrower zig-zag, made the stitches longer, and used a finer thread, it may have looked better.....I commonly use a serpentine stitch when I machine apply my bindings and I like that little scalloped look....

I say trial and error is the only way to see if you are happy with it. Just go for it!!

I use decorative stitches on some quilts I recently made a quilt using a foundation block at the decorative stitch was perfect for the quilting.

I like the serpentine stitch - but not all machines have it.

If the machine does not have the serpentine stitch, I think I would prefer a multi-step zigzag pattern to a one-step zigzag pattern.

I agree with the make a swatch, and try out various patterns.

I like to stitch in the ditch -

Another option would be to quilt next to the ditch using the edge of your walking foot as a guide. When I was hand quilting I sewed next to the ditch.

I made a crazy quilt and I used just about every decorative stitch my machine had in different color threads. I love the way it turned out. There are no rules when quilting. Do whatever is pleasing to your eyes.

I've used a tricot stitch that looks like a zig zag as bearisgray was describing. Comes out cute. On one of my machines (Janome mechanical), if you alter the stitch length and width, it turns into a scallop shape instead of a zig zag. Very attractive on kid quilts and such. Longer stitches like 3 or 3.5 look good. I use a walking foot.

I use the serpentine stitch a lot, especially for my donation quilts. One thought on a wide zigzag, the stich can turn out loose enough for small fingers to slide under. Maybe your machine has the zigzag that stitches a few times on the zig and a few on the zag.