You might want to study a map. Quiberon Bay is a large sheltered body of water on the coast of France. It is one of the largest and best anchorages in Europe.

As for the landing, there is a single second rate German infantry division covering that portion of the French coast. Like several others that were shipped East at the beginning of November to make up for the losses being taken there it was marginally trained and was spending alot of its time building field fortifications.
This division would have had about 36 105mm guns and a dozen 150mm available for artillery at most. It would have had between 18 and 27 antitank guns in varying sizes, most likely 3.7cm and 5 cm as the best equipment was going elsewhere. Radios and field telephones would be in short supply.

An example of this in the East is the 385th ID. In six weeks of combat it lost half its company commanders and five of six battalion commanders. This unit was reported at that point as "ruined for offensive use." The high losses were attributed by the division commander to poor training and inexperianced leadership. This is no different from 90% of what is in AOK 7 in November 42.

There won't be any Pz III or IV, STuG III, 88s or air support for the German defenders for several days. Instead, they will be overextended manning just small unconnected strong points with very limited artillery support.

As for the Allies, they would be ashore with a full armored division of mixed Stuart, M3 Lee, and Sherman tanks. There would be three tank destroyer battalions ashore, one of M10, two of 75mm M3 halftracks. The British tank brigade would be Churchills.

The second wave should add the 1st and 34th US Infantry divisions, along with the 1st Armored division (all in England). The British would send two additional infantry divisions and one armored division.

Since the German response would be to send troops peicemeal into the area initially the best they could hope for is to simply contain the Allies as they did at Anzio and Salerno before that. At Salerno, the Germans threw in 5 panzer and 2 panzergrenadier divisions against just 3 Allied (two British one US) infantry divisions. They also had parity in the air. Yet, they lost and lost badly there.
Allied naval gunfire was unstoppable. The Germans also discovered that ships are not easy things to sink, especially when most of your aircraft are unsuited for the job. On the whole, the Allies would get ashore. Once ashore they, like every time they landed somewhere, would be difficult or impossible to dislodge.

Let's mention Dieppe while we are at it. Had the Allies landed a larger force such as the one proposed here, it too would have succeeded. The German defenders would have been overwhelmed. As it was, it was intended as a large raid and in that it failed like most half measures do.