I'm not a great cook, but I'm betting it was the light butter. Butter/margarine/shortening all make a big difference in the texture of a cookie. If I remember right, butter tends to make a thinner cookie than margarine, & I'm thinking light butter would make it even thinner.

I have been making this recipe for several years now. Some suggestions:

If you want to have thin, soft cookies add more butter and start them more flat than ball-shaped.

If you want nice thick cookies with a soft center, put the dough in the refrigerator for an hour then roll tablespoon size chunks into balls.

A few years ago i noticed some cookie science postings on various sites. Here is one of those...cookie science ...(seriousEats has one as well)

If i want crisp and lacy i also use my steel sheet pan on a higher rack in the oven...as well as more butter/liquid and a bit less flour. Found that out years ago when i bought those steel cookie sheets instead of aluminum and ended up with the wrong cookie...i wanted more soft and chewy but ended up with big flatties than cooked real fast and almost burned. I caught them in time and they became a hit with the crispy cookie lovers.

Lite butter contains more water than real butter....and less fat, some of which may be oil.....and you may have omitted some of the flour.
Also when using baking soda as leavening, unless you bake the cookies right away, the baking soda does it's thing and then goes flat.
To recreate, I would use the lite butter....same brand she had if possible, hold back on at least 1/4 cup of flour until you have baked a few test cookies, and omit the baking sods that causes them to get puffy.

I think y'all have hit all of the variables, including some I didn't think about.

DD's sheet pan may well be steel. It is considerably heavier than mine. Her rack was higher in the oven than mine. I had a pan of cookies in my hands when I noticed it, so I didn't change it.

I didn't want to use the light butter but that was all she had and it was too late in the evening to go to the grocery for more. She said it didn't make a difference in her cooking, but she doesn't bake.

I don't have the same sheet pans, but I will move my rack up a notch; leave out the soda; and cut back on the flour. I've already softened the butter, so I'll use regular butter this time and see what happens, although I think it is really the key to this mystery. (P.S. I have a real problem with "lite" things. My attitude is instead of buying "lite", eat less of the real thing!)

Many thanks to all of you for responding!

I sure agree on the "lite" thing....but you might think about subbing some vegetable oil for some of the butter...think it will make a faltter cookie and you will still get that "real butter" flavor...like sub 1 1/2 T. oil for equal amount of the butter.

First batch is out of the oven. Here is what I did: deleted 2 Tablespoons of butter; added 2 Tablespoons of vegetable oil; reduced flour by appx 1/4 cup (used 151 grams of flour); deleted baking soda. Baked on rack one notch above half-way.

No discernible difference between Sil-pat and parchment paper

I learned from a cookie expert that a teaspoon or two of water can make the entire difference between chewy cookies and crunchy cookies. I think Linda is right that it was the water content in the light butter. Oil makes cookies spread, but it doesn't make them chewy.

A different expert, whose expertise is specifically in chewy flat Toll House cookies, always flattens them on the baking sheet, always adds the water that was in the old version of the recipe, and gets massive raves. He only uses full fat, never ever "lite", but does add the water.

Good luck with the experiments!

I've got about 6 left to cook. I think I'll throw in a bit of water just to see what happens. I tried flattening one batch with my hand before placing in the oven. Didn't seem to make much difference. Where is the old version of the Toll House cookie recipe? I like flat chewy cookies!

Another potential experiment is to get some of the exact light butter and see if you can replicate the ones you made at your daughter's, ceteris paribus.

I can't get hold of the expert. Remind me and I'll get the Toll House recipe from him. Be warned, however, that it's more about knack than recipe. I can come close. A friend once tried to make them, she did everything right, but they were inedible. Since learning from Grainlady about the differences in sugars, I've wondered if she used beet sugar. Oh! You're using the same kind of sugar, right? Because sugar is a water source when it melts and there are big differences between the way cane and beet bake, apparently, even though the chemical difference is very small.

I found this blog, which has excellent cookie advice but it has yet a different version of the recipe which uses part shortening. :) Rather than the combo, I'd use baking margarine (firm stick that has 100 Calories per oz.). Butter will give you a crisper cookie, especially at the edge, with the melt in your mouth quality. Margarine has a higher melt point so is chewier. Some people are anti-margarine, but there is a texture difference. Since you used a version of butter for the original oatmeal cookies, however, there's no reason to think margarine would help replicate it. I don't know about the product you used, but generally, lite is butter whipped (adding air) with added water.

Apparently, the "original" recipe has gone through many iterations. The expert I mentioned uses the recipe that was on the bag when he first started making the cookies, decades ago. If I forget, ask me again, and I'll get it for you. Or just add a teaspoon of water and see what it gets you. :)

bbstx, you don't want to eliminate the baking soda -- that's what will make the cookie spread. Baking powder is what's twice-acting (rise when activated w/ liquid, then rise again when activated w/ heat), not baking soda. I suspect it was the "light" butter that made the biggest difference -- and/or the oven temp and baking pan used.

ETA: you may have added too much b. soda, which would cause it to overspread! But the soft texture has to be accounted for -- probably caused by the light butter... I've never seen light butter, so don't know what's in it. Over-creaming butter & sugar can alter texture too! Humidity could also play a factor. If you want to replicate the recipe, then start by doing exactly what you think you did... everything the same, including using the same light butter. Then decide how to tweak it. I'm pretty good at tweaking recipes because I need to convert to gluten-free.

ah -- I missed plllog's comment about using beet sugar vs cane sugar -- that can make a huge difference in some recipes.

The spoonful of water made no difference. I'll try adding water and subtracting flour next time. And, perhaps, I'll borrow DD's cookie sheets.

Right now, I'm out of gas. I've made 2 large pots of soup, a batch of cookies, and a batch of twice baked potatoes. It doesn't sound like much, but the meat in one batch of soup is tenderloin chain leftover from trimming a couple of whole tenderloins. It took forever to trim the chains of fat and silverskin. All have gone into the freezer except the cookies. I'll take them to DD next time I go. Now I get to clean the kitchen. Yippee!

Sleevendog, I read the article on cookie science, but I haven't had time to watch the Ted Talk, yet. Stella Parks (BraveTart) at Serious Eats wrote about the temperature of butter (60 degrees) in sugar cookies, among other things. I've followed her recipe and her advice with excellent results.

I will try again. May have to bake the cookies at DD's house so I can use her pans, her oven, her sugar, and her "lite" butter. I really hate cooking at someone else's house, but it may be necessary if I want to replicate the Mistake Cookies for DSIL.

Here are the ingredients in the store brand light/lite butter DD had

butter (cream, salt), water, buttermilk, contains less than 2% of: modified tapioca starch, tapioca maltodextrin, salt, distilled monoglycerides, lactic acid, potassium sorbate, and sodium benzoate (preservatives), PGPR, (emulsifier), natural flavor, xanthan gum, vitamin a palmitate, beta carotene (color).

For comparison, here are the ingredients in Land O Lakes Unsalted Butter: Sweet Cream, Natural Flavoring.

I don't understand why someone who tries to eat healthfully, and she truly does, would eat light butter.

Baking soda does not make baked goods spread...it does just the opposite, makes them rise up....not out.
Another possibility might be the parchment. I feel that cookies spread most on one stainless cookie sheet without parchment nor silpat.
( bought when I didn't know better....but it serves to carry food to the grill ect)

Several old cookie recipes I have call for 2 teaspoons of water or 2 teaspoons of water beaten with the eggs.

Baking soda causes spread. b. soda vs b. powder

Linda may have put her finger on it: TWO teaspoons of water, rather than one. That would depend on batch size, of course, but since one wasn't sufficient. I wouldn't reduce the flour. Use the same amount as you used before, and the same kind (KA AP, for instance, is heavier than Gold Medal or Pillsbury's Best (though I think those two are pretty interchangeable).

Come to think of it...were the oats the same? Were yours drier?

The reason you may THINK baking soda causes spread, it it reacts as soon as moisture is added to the baking soda and brown sugar, and unless you add baking powder too, which reacts with heat, the baking soda has likely spent itself by the time you get the cookies shaped.
My old old sugar cookei recipe calls for some...forget how much, milk to be added as does my Toll house cookie recipe....and I did have a recipe from the Aunt Sally Spry cook book ( now I am really dating myself!!) for a sugar cookie that called for some milk

I think the oats were the same, just basic old-fashioned Quaker Oats. I have no idea what brand of flour DD uses, and I'll bet she doesn't know either. I'm pretty sure it would be a standard grocery brand, like Pillsbury or Gold Medal or possibly the store brand.

I'm so averse to scrubbing pans, I'm certain I used parchment paper at DD's.

I only had 4 cookies left when I added the water. I think the recipe makes 30 cookies. I will need to add greater than 2 1/2 teaspoons of liquid to make a difference.

As DD said, even though these may not be the Mistake Cookies, they'll get eaten quickly!

Yep....cookies have a way of disappearing.

So I got hold of the Toll House cookie expert, but he wasn't quite coherent. He said that the old bag said half a tsp. of water (3/4 lb. chips), but that he doesn't always use it and it depends on how wet the sugar is, the eggs, etc. Which goes back to knack. He uses Gold Medal AP, the 100 Calorie margarine baking sticks, and C&H cane sugar (though I imagine it's no different from other cane sugars), and always Nestle's chips.

The most important part, he says, for chewy cookies is the baking. They must be flattened and not overbaked. It's the same story as in the blog I linked--if you wait until the cookies are completely done to take them out of the oven, they're overdone. The edges need to be set and going golden but the center should look like it needs another minute or two. It'll finish baking in its own heat.

Re the oatmeal cookies, I used to make the Betty Crocker recipe I think, with raisins but never with nuts. They came out chewy, but I don't know what the differences are. I haven't made oatmeal cookies in a long time.

What size eggs did she have? Most recipes call for large, if she had extra large or jumbo, that would be more egg.

My bet is on the artificial butter.

This discussion made me think of a classic I haven't had in years: oatmeal lace cookies. They spread out very thin when baked...

http://www.marthastewart.com/313866/oatmeal-lace-cookies

When you mentioned 'thin as a lace cookie, pliable and sticky," I thought along the same lines as Carol_w_fl.

Too bad none of us were there to see where exactly your cookies took a turn for . . . the better ☺

First, I would find out if the 'light' butter used might've been vegan 'butter' (whose main ingredients are vegetable oil and water).

In which case, I would avoid adding more water to your recipe, because while adding more liquid will make the cookie spread, it will also make it too delicate.

Replicate every step you remember, except, reduce the amount of flour by half. But keep the 3 cups of oatmeal the same.

To avoid 'ruining' an entire batch of cookies, prepare the recipe as indicated on the Quaker Oats box, but reserve half of the (combined) dry ingredients, and set aside. Then, add only half the flour mixture to the butter/sugar/egg mixture.

Bake only one or two cookies (on parchment paper) to test for consistency. You should get what you're looking for. If not, add the reserved flour mixture to the cookie batter, and proceed as directed.

But, if you end up with another happy mistake, you'd better build a wall around it.

Sol

Check the oven temperature. Might not have been 350F.

At 300F, the cookies were soft enough to spread but not cooked to crispy, just pliable.

dcarch