Years ago, 40 something, I took basic sewing lessons from a great teacher. If you could sew a shirtwaist dress with cuffs and collar, you could sew any garment. I tailored for years, 5/8" seam allowance. I was taught by her to concentrate on the seam allowance, not the needle. Then I started quilting. I had to get that 1/4" seam allowance. I used white adhesive tape, used with bandages. I taped that down to my machine and I had no more trouble. You know the needle is set because you started to sew, then watch your seam allowance because the sewing will continue until you stop. I did not have any more trouble. And I have 7 machines but I am not telling anyone. No one saw that in this writing. haha

Nobody has mentioned the quilter's "scant" 1/4 inch. I find that most patterns really mean to use a scant 1/4 inch seam. This measurement takes into account the needle size and thread width of your particular set up. I have learned that using my 1/4 foot but sewing a slightly less 1/4 inch seam works best for me. By slightly less, I mean maybe a thread or couple of thread widths less than 1/4 inch. If you measure your finished size, I think you might be happier. I have never used Bonnie Hunter's tool, but I have thought about purchasing one just to have when changing machines. Try sewing slightly less, a "scant" measurement and see if this helps. Hope it does!

I bought a 1/4" foot with guide specifically for my Viking at one point thinking it would help. Not! I have a 'scant 1/4' setting on my machine that works much better. Returned the foot. I also am of the school that keeps my finger on the left edge of my foot and gently guide my fabric through. I also agree that consistency is usually far more important than precision 100% of the time.

I ended up making a block a couple of times with different needle settings until the block came out exact.
Then I wrote the setting on my machine. No more problems, my machine is set at 2.3 for 1/4 inch.
You can do it with a simple strip set also.

I always watch the edge of the fabric ahead of the foot & try to keep that where it should be - that is what I was taught when Mom taught me to sew as a small child - so small I couldn't reach the treadle - she belted a box to the treadle for me to use - lol

I found that using thinner bobbin thread helped with the "scant" quarter inch. Also, adjusting my needle so that it sewed the width of an index card line helped, as well. Good luck as you continue your quilting journey.

I learned to concentrate on where my hand is in guiding that last inch from a Serger instructor. She pointed out that most of us unconsciously pull the fabric to the left, then running off the edge of the fabric. She told us to never put our hand beyond the needle on serging, so then I started watching my hand when coming to the end of my piecing on my sewing machine.....yep, I was pulling the piece slightly to the left. So I started using a stylus to hold my piece at the end so it did not veer off and was held close to the 1/4" marking. It works. Also, I don't sew a 1/4" any more, I use a scant 1/4, my piecing seems to go together better and I am not short fabric when squaring up the block....I would rather trim a block then not have enough and have to unsew lots of pieces.

The "pointy tool" works for me. I was always wandering at the end of a seam. It' didn't matter much when I was doing 6 inch squares for charity quilts, but it matters a lot when you have smaller pieces.
You can buy a stylus for a lot of money, use a chopstick from your Chinese meal, or use a bamboo skewer. The skewers are way too long, so I cut mine in half or less (my kitchen scissors will do that) and put them in the pencil sharpener. A very gentle push into the sharpener will get it as sharp as you like. I sharpen both ends this way. I have one with each machine and have given some away to others.
Happy sewing!

I also had that problem when I began quilting. I figured out it was the machine I was using. I invested in a new machine and do not have that problem. It was a foot pressure problem. Now I get perfect quarter inch seams.

I have always struggled with an accurate quarter inch seam, and I have tried everything listed so far plus numerous different feet. What's made the difference for me is getting a new machine. I find if I set the stitch width to 6, I get a perfect quarter inch. My last machine couldn't go wider than 5. It's taken me a decade to get this worked out!