A “quiet” oven is likely around 325° to 375°.
The two main resources I’ve used are the Internet Archive and Michigan State University’s Sliker Culinary Collection.
The term “quiet oven” does not appear to be as common as other terms such as slow, moderate, or quick, but it does appear in older cookbooks. The Internet Archive has entries that include the term from 1853 and into the 1900s, though some of the latter ones are reprints of earlier recipes.
Newspapers.com also shows several recipes that call for a “quiet oven”, including one “relatively quiet oven”. I’m pretty sure it provided more mistaken “quick oven” and “quiet even” hits as “quiet oven” than valid “quiet oven” hits, but “quiet oven” clearly was a term used when sharing recipes with readers.
The earliest reference I found on the Internet Archive is Miss Crawford’s 1853 French Cookery Adapted for English Families; on page 181 her Petits Patés Hot recipe reads:
Having prepared your paste as directed, roll it out very thin, cut it out with a paste-cutter in rounds as large as a crown piece, put two or three rounds one on the other, with a little minced meat, of what kind you please in each, cover it, moisten the edges with beaten yolk of egg, egg them over, and bake in a quiet oven.
Later, Margaret Black’s 1882 Household Cookery and Laundry Work has at least three references to a quiet oven. From page 95,
Light sponge cakes, and all light cakes, must have a quiet oven, as well as all large cakes which contain much baking powder.
And two on facing pages on 100-101:
Mix thoroughly, and pour into a prepared tin, and bake till ready in a quiet oven.
Butter a cake-tin and dust it with fine sugar; pour in the mixture, and bake in a very quiet oven till ready—about half-an-hour, perhaps.
The term even appears in a poem by Walter Eldred Warde, in his 1885 Lines Grave and Gray. Look on page 93 for “What Might Be”, a poem to the muffin man. “In quiet oven you do bake…”.
There is one clue to the temperature that quiet ovens represented in the September 5, 1896 London Reader of Literature, Science, Art and General Information. On page 503 (I think), there are answers to correspondence. One answer specifically contrasts a “very quiet oven” to ovens that are “too hot”:
GINGER.—The reason your loaf sinks in the middle is that your oven may be too hot; gingerbread requires a very quiet oven; you see the treacle melts and so does the sugar, and if your oven is too hot it cooks quickly round the edges and draws the flour away from the middle; when eggs are in it they more quickly cook, and to some extent prevent it sinking; probably in your plain gingerbread you have scarcely enough flour; a little more would make it all right.
Bob Brown’s 1955 The Complete Book of Cheese states on page 118 that a quiet oven is a moderate oven:
Bake 1 hour in a “quiet” oven, as the English used to say for a moderate one, and when done set aside for 12 hours before eating.
And in his 2011 Small Adventures in Cooking James Ramsden writes about a vintage recipe:
It also suggests that sponge should be baked in ‘a quiet oven’, which is a lovely but useless instruction, bless.
His version of the recipe uses an oven temperature of 170°C, or 338°F.
Early oven manuals occasionally contained conversion charts, tables that both corresponded older terms to modern temperatures and tables that corresponded baked goods to specific temperatures. I was unable to find any that include “quiet” in their tables. Many do contain “moderate” and “gingerbread”, however. The latter are surprisingly consistent.
Occident Flour’s ca. 1920 Occident Cake Recipes, on page 3, places gingerbread under the column for “slow” ovens, or “250°F.—325°F.—350°F.”. Both the ca. 1925 Universal Electric Range Instruction Cook Book and Pyrofax Gas’s ca. 1930 Cooking Made Easier place gingerbread at 350° in their charts on pages 15 and 32, respectively.
Even the more common terms are all over the place in these charts. They were never specific to begin with. Calumet Baking Powder’s 1923 Modern Biscuit Making calls for baking in a moderate oven that is 325° F on page 12, and then a moderate oven of 350° F across the fold on page 13.
That’s expected. But even the ranges given in oven manuals vary. The ca. 1925 Universal Electric Range Instruction Cook Book places moderate ovens at 325° to 400°. The ca. 1925 Monarch Electric Cook Book places moderate ovens very tightly at “350 to 360 Degrees F.” on page 68. They loosen up in their ca. 1930 Monarch Electric Range Instruction Book to “350 to 400 Degrees F.”. Frigidaire in ca. 1950 puts moderate at 325°F to 375°F and then in 1961 at 350° to 375°F.
The Merriam-Webster dictionary combines them all into a definition for moderate oven of “an oven heated to a temperature between 325° and 400° F”.
So even if a table from the transition period to temperatures could be found that includes the term “quiet oven”, it would likely be just as subjective.
Many oven manuals did not contain a conversion chart. At least one actively denigrated the terms for being too subjective to use. The Estate Stove Company’s 1925 Estate Cook Book begins on page 2 with:
CULINARY efficiency demands the complete elimination of guesswork and rule-o’-thumb methods in baking and roasting.
Such terms as “slow” oven, “fast” oven, “moderate” oven are not found in modern cook-books. They are too hazy and indefinite. Instead, exact temperatures are specified.
Such homely, old-fashioned expedients as testing the oven by a piece of manila paper—“when it becomes the proper shade of brown,” or by a teaspoonful of flour—“if it browns while I count forty, the oven is just hot enough for bread,” are merely poor makeshifts. There is nothing scientific about them; nothing accurate; nothing certain; nothing dependable.
Unsurprisingly their cook book does not contain a conversion chart. Why would it? Any such chart would be inaccurate, uncertain, and undependable!
The Estate Cook Book’s two gingerbreads (page 10) bake at 350 and at 325.
The clues I’ve found are somewhat contradictory, at least potentially. Is the “very quiet oven” that is required for gingerbread going to have a higher or lower temperature than a merely “quiet” oven? Because the author is telling the questioner that they were probably using too hot of an oven, I suspect that “very” quiet means cooler rather than hotter. If so, and if a gingerbread’s 325° to 350° is a “very quiet” oven, then a merely “quiet” oven would likely be 350° to 375°.
This somewhat matches James Ramsden’s 170C which is likely to be translated to either 325F or 350F, since recipes that use Fahrenheit tend to use even multiples of 25.
A range of 325°F to 375°F or perhaps 350°F to 375°F for a quiet oven fits roughly with Bob Brown’s correspondence of “quiet” and “moderate” as well.
So, while it’s important to remember that such terms are necessarily vague, it is likely that a “quiet oven” is around 325°F to 375°F.